definite assignment

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What’s the difference between definite assignment assertion and ambient declaration?

When asserting that a field is definitely initialized in a class, what’s the difference between ! (exclamation point, definite assignment assertion) and the declare modifier?

The following code is an error in strict mode since TS doesn’t know for sure that the field has been initialized.

I’ve seen 2 ways of handling this:

• Definite assignment assertion: class Person { name!: string; }
• Ambient declaration: class Person { declare name: string; }

I can’t see the difference between these two techniques. They both cure the error, they both don’t emit code, and they both don’t allow initializers. Does ambient declaration (released in v3.7) simply outdate definite assignment (released in v2.7)? Should declare be used instead of ! whenever possible?

• initialization
• type-assertion
• typescript-class

Declare is mainly useful for mocking values when playing around with the type system. In production code, it's rarely used.

This says to the compiler:

"There is a property called name of type string . I shouldn't have to prove to you that name actually exists, but I want to use it anyway."

The declare keyword is typically used in type definition files that provide typings for files that Typescript cannot get type information from (such as plain JS files). So if I was reading your code, I would assume that name is getting monkey patched in from some JS file somewhere, and you are noting that here.

I would be incorrect.

"There is a property called name with a type of string | undefined . It starts with a value of undefined . But every time I get or set that property, I want to treat it as type string ."

Using this form it's clear to anyone reading the code that name is undefined at first, but is treated like a string anyway. That means it must be set in this file somewhere, just probably not in the constructor.

From what you are saying, I would be correct in those assumptions.

In practice, in this particular case , the result is nearly identical. In both cases you have a string property that you never have to actually initialize. However, I would argue that the name!: string is far more clear about what is actually going on.

Also, declare never emits code. It makes something only exist in the type system. (Thanks for mentioning this @NoelDeMartin)

Compiles to:

Note that baz is completely absent from the output.

Lastly though, I have to mention, you should probably just refactor your code so that you can assign the property in the constructor. Both those methods are not as type safe since you could potentially treat an uninitialized value as a string , which will likely cause a crash if it happens.

• 3 I've been running into an issue recently that was solved by using declare instead of the assertion. That is to say, there is some difference in practice depending on your configuration. For example, I'm using esnext target and this activates the useDefineForClassFields configuration. Here's an example in the Typescript playground showcasing how the output is different: typescriptlang.org/play?useDefineForClassFields=true#code/… –  Noel De Martin Commented Jan 14, 2022 at 16:31

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Definition of assignment

task , duty , job , chore , stint , assignment mean a piece of work to be done.

task implies work imposed by a person in authority or an employer or by circumstance.

duty implies an obligation to perform or responsibility for performance.

job applies to a piece of work voluntarily performed; it may sometimes suggest difficulty or importance.

chore implies a minor routine activity necessary for maintaining a household or farm.

stint implies a carefully allotted or measured quantity of assigned work or service.

assignment implies a definite limited task assigned by one in authority.

Examples of assignment in a Sentence

These examples are programmatically compiled from various online sources to illustrate current usage of the word 'assignment.' Any opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback about these examples.

Word History

see assign entry 1

14th century, in the meaning defined at sense 1

Phrases Containing assignment

• self - assignment

Dictionary Entries Near assignment

Cite this entry.

“Assignment.” Merriam-Webster.com Dictionary , Merriam-Webster, https://www.merriam-webster.com/dictionary/assignment. Accessed 17 Jul. 2024.

Legal Definition

Legal definition of assignment, more from merriam-webster on assignment.

Nglish: Translation of assignment for Spanish Speakers

Britannica English: Translation of assignment for Arabic Speakers

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Definite Assignment

16.1 definite assignment and expressions, 16.1.1 boolean constant expressions, 16.1.2 boolean-valued expressions, 16.1.3 the boolean operator &&, 16.1.4 the boolean operator ||, 16.1.5 the boolean operator , 16.1.6 the boolean operator &, 16.1.7 the boolean operator |, 16.1.8 the boolean operator ^, 16.1.9 the boolean operator ==, 16.1.10 the boolean operator =, 16.1.11 the boolean operator :, 16.1.12 the conditional operator :, 16.1.13 boolean assignment expressions, 16.1.14 other assignment expressions, 16.1.15 operators ++ and --, 16.1.16 other expressions, 16.2 definite assignment and statements, 16.2.1 empty statements, 16.2.2 blocks, 16.2.3 local variable declaration statements, 16.2.4 labeled statements, 16.2.5 expression statements, 16.2.6 if statements, 16.2.7 switch statements, 16.2.8 while statements, 16.2.9 do statements, 16.2.10 for statements, 16.2.10.1 initialization part, 16.2.10.2 incrementation part, 16.2.11 break , continue , return , and throw statements, 16.2.12 synchronized statements, 16.2.13 try statements.

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Control statements, java object class, java inheritance, java polymorphism, java abstraction, java encapsulation, java oops misc.

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[ uh - sahyn -m uh nt ]

She completed the assignment and went on to other jobs.

Synonyms: job , obligation

He left for his assignment in the Middle East.

• an act of assigning; appointment.
• the transference of a right, interest, or title, or the instrument of transfer.
• a transference of property to assignees for the benefit of creditors.

/ əˈsaɪnmənt /

• something that has been assigned, such as a mission or task
• a position or post to which a person is assigned
• the act of assigning or state of being assigned

assignment of a lease

• the document effecting such a transfer
• the right, interest, or property transferred
• law (formerly) the transfer, esp by an insolvent debtor, of property in trust for the benefit of his creditors
• logic a function that associates specific values with each variable in a formal expression
• history a system (1789–1841) whereby a convict could become the unpaid servant of a freeman

Other Words From

• misas·signment noun
• nonas·signment noun
• reas·signment noun

Word History and Origins

Origin of assignment 1

Synonym Study

Example sentences.

Yariel Valdés González and I faced these challenges while on assignment in South Florida and the Deep South from July 21-Aug.

They’re putting time into decoration just as they would in their physical classroom, and students can interact with the space by, say, clicking on a bookshelf to get a reading assignment.

For now, if the district moves to in-person learning, instruction in Carlsbad will take place on campus five days per week and students may engage in additional independent practices and other assignments at home.

The assignments must also respect the relationships between the elements in the group.

It’s very hard, by the way, to do real random assignment studies of couples therapy.

His most recent assignment was the 84th Precinct, at the Brooklyn end of the Brooklyn Bridge.

When Lewis was shipped off to Vietnam, his son was just three months old, and the timing of the assignment worried Lewis.

When Vial got that first assignment, she was just beginning her photography career, and Cirque du Soleil was only a few years old.

“For our winter issue, we gave ourselves one assignment: Break The Internet,” wrote Paper.

By the 1950s the rapid assignment of gender to an ambiguously gendered infant had become standard.

Consent to an assignment may be given by the president of the company, without formal vote by the directors.

A transfer by the lessee of the whole or a part of his interest for a part of the time is a sublease and not an assignment.

An assignment to one who has an insurable interest as relative, creditor and the like, is always valid.

When an assignment of it is made, the assignee may sue in his own name for rent accruing after the assignment.

In some states statutes forbid the assignment of such policies for the benefit of creditors.

Related Words

• appointment

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TypeScript 2.7

Constant-named properties.

TypeScript 2.7 adds support for declaring const-named properties on types including ECMAScript symbols.

This also applies to numeric and string literals.

unique symbol

To enable treating symbols as unique literals a new type unique symbol is available. unique symbol is a subtype of symbol , and are produced only from calling Symbol() or Symbol.for() , or from explicit type annotations. The new type is only allowed on const declarations and readonly static properties, and in order to reference a specific unique symbol, you’ll have to use the typeof operator. Each reference to a unique symbol implies a completely unique identity that’s tied to a given declaration.

Because each unique symbol has a completely separate identity, no two unique symbol types are assignable or comparable to each other.

Strict Class Initialization

TypeScript 2.7 introduces a new flag called strictPropertyInitialization . This flag performs checks to ensure that each instance property of a class gets initialized in the constructor body, or by a property initializer. For example

In the above, if we truly meant for baz to potentially be undefined , we should have declared it with the type boolean | undefined .

There are certain scenarios where properties can be initialized indirectly (perhaps by a helper method or dependency injection library), in which case you can use the new definite assignment assertion modifiers for your properties (discussed below).

Keep in mind that strictPropertyInitialization will be turned on along with other strict mode flags, which can impact your project. You can set the strictPropertyInitialization setting to false in your tsconfig.json ’s compilerOptions , or --strictPropertyInitialization false on the command line to turn off this checking.

Definite Assignment Assertions

The definite assignment assertion is a feature that allows a ! to be placed after instance property and variable declarations to relay to TypeScript that a variable is indeed assigned for all intents and purposes, even if TypeScript’s analyses cannot detect so.

With definite assignment assertions, we can assert that x is really assigned by appending an ! to its declaration:

In a sense, the definite assignment assertion operator is the dual of the non-null assertion operator (in which expressions are post-fixed with a ! ), which we could also have used in the example.

In our example, we knew that all uses of x would be initialized so it makes more sense to use definite assignment assertions than non-null assertions.

Fixed Length Tuples

In TypeScript 2.6 and earlier, [number, string, string] was considered a subtype of [number, string] . This was motivated by TypeScript’s structural nature; the first and second elements of a [number, string, string] are respectively subtypes of the first and second elements of [number, string] . However, after examining real world usage of tuples, we noticed that most situations in which this was permitted was typically undesirable.

In TypeScript 2.7, tuples of different arities are no longer assignable to each other. Thanks to a pull request from Kiara Grouwstra , tuple types now encode their arity into the type of their respective length property. This is accomplished by leveraging numeric literal types, which now allow tuples to be distinct from tuples of different arities.

Conceptually, you might consider the type [number, string] to be equivalent to the following declaration of NumStrTuple :

Note that this is a breaking change for some code. If you need to resort to the original behavior in which tuples only enforce a minimum length, you can use a similar declaration that does not explicitly define a length property, falling back to number .

Note that this does not imply tuples represent immutable arrays, but it is an implied convention.

Improved type inference for object literals

TypeScript 2.7 improves type inference for multiple object literals occurring in the same context. When multiple object literal types contribute to a union type, we now normalize the object literal types such that all properties are present in each constituent of the union type.

Previously type {} was inferred for obj and the second line subsequently caused an error because obj would appear to have no properties. That obviously wasn’t ideal.

Multiple object literal type inferences for the same type parameter are similarly collapsed into a single normalized union type:

Improved handling of structurally identical classes and instanceof expressions

TypeScript 2.7 improves the handling of structurally identical classes in union types and instanceof expressions:

• Structurally identical, but distinct, class types are now preserved in union types (instead of eliminating all but one).
• Union type subtype reduction only removes a class type if it is a subclass of and derives from another class type in the union.
• Type checking of the instanceof operator is now based on whether the type of the left operand derives from the type indicated by the right operand (as opposed to a structural subtype check).

This means that union types and instanceof properly distinguish between structurally identical classes.

Type guards inferred from in operator

The in operator now acts as a narrowing expression for types.

For a n in x expression, where n is a string literal or string literal type and x is a union type, the “true” branch narrows to types which have an optional or required property n , and the “false” branch narrows to types which have an optional or missing property n .

Support for import d from "cjs" from CommonJS modules with --esModuleInterop

TypeScript 2.7 updates CommonJS/AMD/UMD module emit to synthesize namespace records based on the presence of an __esModule indicator under esModuleInterop . The change brings the generated output from TypeScript closer to that generated by Babel.

Previously CommonJS/AMD/UMD modules were treated in the same way as ES6 modules, resulting in a couple of problems. Namely:

• TypeScript treats a namespace import (i.e. import * as foo from "foo" ) for a CommonJS/AMD/UMD module as equivalent to const foo = require("foo") .Things are simple here, but they don’t work out if the primary object being imported is a primitive or a class or a function. ECMAScript spec stipulates that a namespace record is a plain object, and that a namespace import ( foo in the example above) is not callable, though allowed by TypeScript
• Similarly a default import (i.e. import d from "foo" ) for a CommonJS/AMD/UMD module as equivalent to const d = require("foo").default .Most of the CommonJS/AMD/UMD modules available today do not have a default export, making this import pattern practically unusable to import non-ES modules (i.e. CommonJS/AMD/UMD). For instance import fs from "fs" or import express from "express" are not allowed.

Under the new esModuleInterop these two issues should be addressed:

• A namespace import (i.e. import * as foo from "foo" ) is now correctly flagged as uncallable. Calling it will result in an error.
• Default imports to CommonJS/AMD/UMD are now allowed (e.g. import fs from "fs" ), and should work as expected.

Note: The new behavior is added under a flag to avoid unwarranted breaks to existing code bases. We highly recommend applying it both to new and existing projects. For existing projects, namespace imports ( import * as express from "express"; express(); ) will need to be converted to default imports ( import express from "express"; express(); ).

With esModuleInterop two new helpers are generated __importStar and __importDefault for import * and import default respectively. For instance input like:

Will generate:

Numeric separators

TypeScript 2.7 brings support for ES Numeric Separators . Numeric literals can now be separated into segments using _ .

Cleaner output in --watch mode

TypeScript’s --watch mode now clears the screen after a re-compilation is requested.

Prettier --pretty output

TypeScript’s pretty flag can make error messages easier to read and manage. pretty now uses colors for file names, diagnostic codes, and line numbers. File names and positions are now also formatted to allow navigation in common terminals (e.g. Visual Studio Code terminal).

Nightly Builds

How to use a nightly build of TypeScript

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Last updated: Jul 17, 2024  

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9 Variables

• 10 contributors

9.1 General

Variables represent storage locations. Every variable has a type that determines what values can be stored in the variable. C# is a type-safe language, and the C# compiler guarantees that values stored in variables are always of the appropriate type. The value of a variable can be changed through assignment or through use of the ++ and -- operators.

A variable shall be definitely assigned ( §9.4 ) before its value can be obtained.

As described in the following subclauses, variables are either initially assigned or initially unassigned . An initially assigned variable has a well-defined initial value and is always considered definitely assigned. An initially unassigned variable has no initial value. For an initially unassigned variable to be considered definitely assigned at a certain location, an assignment to the variable shall occur in every possible execution path leading to that location.

9.2 Variable categories

9.2.1 general.

C# defines eight categories of variables: static variables, instance variables, array elements, value parameters, input parameters, reference parameters, output parameters, and local variables. The subclauses that follow describe each of these categories.

Example : In the following code class A { public static int x; int y; void F(int[] v, int a, ref int b, out int c, in int d) { int i = 1; c = a + b++ + d; } } x is a static variable, y is an instance variable, v[0] is an array element, a is a value parameter, b is a reference parameter, c is an output parameter, d is an input parameter, and i is a local variable. end example

9.2.2 Static variables

A field declared with the static modifier is a static variable. A static variable comes into existence before execution of the static constructor ( §15.12 ) for its containing type, and ceases to exist when the associated application domain ceases to exist.

The initial value of a static variable is the default value ( §9.3 ) of the variable’s type.

For the purposes of definite-assignment checking, a static variable is considered initially assigned.

9.2.3 Instance variables

9.2.3.1 general.

A field declared without the static modifier is an instance variable.

9.2.3.2 Instance variables in classes

An instance variable of a class comes into existence when a new instance of that class is created, and ceases to exist when there are no references to that instance and the instance’s finalizer (if any) has executed.

The initial value of an instance variable of a class is the default value ( §9.3 ) of the variable’s type.

For the purpose of definite-assignment checking, an instance variable of a class is considered initially assigned.

9.2.3.3 Instance variables in structs

An instance variable of a struct has exactly the same lifetime as the struct variable to which it belongs. In other words, when a variable of a struct type comes into existence or ceases to exist, so too do the instance variables of the struct.

The initial assignment state of an instance variable of a struct is the same as that of the containing struct variable. In other words, when a struct variable is considered initially assigned, so too are its instance variables, and when a struct variable is considered initially unassigned, its instance variables are likewise unassigned.

9.2.4 Array elements

The elements of an array come into existence when an array instance is created, and cease to exist when there are no references to that array instance.

The initial value of each of the elements of an array is the default value ( §9.3 ) of the type of the array elements.

For the purpose of definite-assignment checking, an array element is considered initially assigned.

9.2.5 Value parameters

A parameter declared without an in , out , or ref modifier is a value parameter .

A value parameter comes into existence upon invocation of the function member (method, instance constructor, accessor, or operator) or anonymous function to which the parameter belongs, and is initialized with the value of the argument given in the invocation. A value parameter normally ceases to exist when execution of the function body completes. However, if the value parameter is captured by an anonymous function ( §12.19.6.2 ), its lifetime extends at least until the delegate or expression tree created from that anonymous function is eligible for garbage collection.

For the purpose of definite-assignment checking, a value parameter is considered initially assigned.

9.2.6 Reference parameters

A parameter declared with a ref modifier is a reference parameter .

A reference parameter is a reference variable ( §9.7 ) which comes into existence upon invocation of the function member, delegate, anonymous function, or local function and its referent is initialized to the variable given as the argument in that invocation. A reference parameter ceases to exist when execution of the function body completes. Unlike value parameters a reference parameter shall not be captured ( §9.7.2.9 ).

The following definite-assignment rules apply to reference parameters.

Note : The rules for output parameters are different, and are described in ( §9.2.7 ). end note

• A variable shall be definitely assigned ( §9.4 ) before it can be passed as a reference parameter in a function member or delegate invocation.
• Within a function member or anonymous function, a reference parameter is considered initially assigned.

For a struct type, within an instance method or instance accessor ( §12.2.1 ) or instance constructor with a constructor initializer, the this keyword behaves exactly as a reference parameter of the struct type ( §12.8.13 ).

9.2.7 Output parameters

A parameter declared with an out modifier is an output parameter .

An output parameter is a reference variable ( §9.7 ) which comes into existence upon invocation of the function member, delegate, anonymous function, or local function and its referent is initialized to the variable given as the argument in that invocation. An output parameter ceases to exist when execution of the function body completes. Unlike value parameters an output parameter shall not be captured ( §9.7.2.9 ).

The following definite-assignment rules apply to output parameters.

Note : The rules for reference parameters are different, and are described in ( §9.2.6 ). end note

• A variable need not be definitely assigned before it can be passed as an output parameter in a function member or delegate invocation.
• Following the normal completion of a function member or delegate invocation, each variable that was passed as an output parameter is considered assigned in that execution path.
• Within a function member or anonymous function, an output parameter is considered initially unassigned.
• Every output parameter of a function member, anonymous function, or local function shall be definitely assigned ( §9.4 ) before the function member, anonymous function, or local function returns normally.

9.2.8 Input parameters

A parameter declared with an in modifier is an input parameter .

An input parameter is a reference variable ( §9.7 ) which comes into existence upon invocation of the function member, delegate, anonymous function, or local function and its referent is initialized to the variable_reference given as the argument in that invocation. An input parameter ceases to exist when execution of the function body completes. Unlike value parameters an input parameter shall not be captured ( §9.7.2.9 ).

The following definite assignment rules apply to input parameters.

• A variable shall be definitely assigned ( §9.4 ) before it can be passed as an input parameter in a function member or delegate invocation.
• Within a function member, anonymous function, or local function an input parameter is considered initially assigned.

9.2.9 Local variables

A local variable is declared by a local_variable_declaration , declaration_expression , foreach_statement , or specific_catch_clause of a try_statement . A local variable can also be declared by certain kinds of pattern s ( §11 ). For a foreach_statement , the local variable is an iteration variable ( §13.9.5 ). For a specific_catch_clause , the local variable is an exception variable ( §13.11 ). A local variable declared by a foreach_statement or specific_catch_clause is considered initially assigned.

A local_variable_declaration can occur in a block , a for_statement , a switch_block , or a using_statement . A declaration_expression can occur as an out argument_value , and as a tuple_element that is the target of a deconstructing assignment ( §12.21.2 ).

The lifetime of a local variable is the portion of program execution during which storage is guaranteed to be reserved for it. This lifetime extends from entry into the scope with which it is associated, at least until execution of that scope ends in some way. (Entering an enclosed block , calling a method, or yielding a value from an iterator block suspends, but does not end, execution of the current scope.) If the local variable is captured by an anonymous function ( §12.19.6.2 ), its lifetime extends at least until the delegate or expression tree created from the anonymous function, along with any other objects that come to reference the captured variable, are eligible for garbage collection. If the parent scope is entered recursively or iteratively, a new instance of the local variable is created each time, and its initializer, if any, is evaluated each time.

Note : A local variable is instantiated each time its scope is entered. This behavior is visible to user code containing anonymous methods. end note

Note : The lifetime of an iteration variable ( §13.9.5 ) declared by a foreach_statement is a single iteration of that statement. Each iteration creates a new variable. end note

Note : The actual lifetime of a local variable is implementation-dependent. For example, a compiler might statically determine that a local variable in a block is only used for a small portion of that block. Using this analysis, the compiler could generate code that results in the variable’s storage having a shorter lifetime than its containing block. The storage referred to by a local reference variable is reclaimed independently of the lifetime of that local reference variable ( §7.9 ). end note

A local variable introduced by a local_variable_declaration or declaration_expression is not automatically initialized and thus has no default value. Such a local variable is considered initially unassigned.

Note : A local_variable_declaration that includes an initializer is still initially unassigned. Execution of the declaration behaves exactly like an assignment to the variable ( §9.4.4.5 ). Using a variable before its initializer has been executed; e.g., within the initializer expression itself or by using a goto_statement which bypasses the initializer; is a compile-time error: goto L; int x = 1; // never executed L: x += 1; // error: x not definitely assigned Within the scope of a local variable, it is a compile-time error to refer to that local variable in a textual position that precedes its declarator. end note

9.2.9.1 Discards

A discard is a local variable that has no name. A discard is introduced by a declaration expression ( §12.17 ) with the identifier _ ; and is either implicitly typed ( _ or var _ ) or explicitly typed ( T _ ).

Note : _ is a valid identifier in many forms of declarations. end note

Because a discard has no name, the only reference to the variable it represents is the expression that introduces it.

Note : A discard can however be passed as an out argument, allowing the out parameter to denote its associated storage location. end note

A discard is not initially assigned, so it is always an error to access its value.

Example : _ = "Hello".Length; (int, int, int) M(out int i1, out int i2, out int i3) { ... } (int _, var _, _) = M(out int _, out var _, out _); The example assumes that there is no declaration of the name _ in scope. The assignment to _ shows a simple pattern for ignoring the result of an expression. The call of M shows the different forms of discards available in tuples and as out parameters. end example

9.3 Default values

The following categories of variables are automatically initialized to their default values:

• Static variables.
• Instance variables of class instances.
• Array elements.

The default value of a variable depends on the type of the variable and is determined as follows:

• For a variable of a value_type , the default value is the same as the value computed by the value_type ’s default constructor ( §8.3.3 ).
• For a variable of a reference_type , the default value is null .

Note : Initialization to default values is typically done by having the memory manager or garbage collector initialize memory to all-bits-zero before it is allocated for use. For this reason, it is convenient to use all-bits-zero to represent the null reference. end note

9.4 Definite assignment

9.4.1 general.

At a given location in the executable code of a function member or an anonymous function, a variable is said to be definitely assigned if the compiler can prove, by a particular static flow analysis ( §9.4.4 ), that the variable has been automatically initialized or has been the target of at least one assignment.

Note : Informally stated, the rules of definite assignment are: An initially assigned variable ( §9.4.2 ) is always considered definitely assigned. An initially unassigned variable ( §9.4.3 ) is considered definitely assigned at a given location if all possible execution paths leading to that location contain at least one of the following: A simple assignment ( §12.21.2 ) in which the variable is the left operand. An invocation expression ( §12.8.9 ) or object creation expression ( §12.8.16.2 ) that passes the variable as an output parameter. For a local variable, a local variable declaration for the variable ( §13.6.2 ) that includes a variable initializer. The formal specification underlying the above informal rules is described in §9.4.2 , §9.4.3 , and §9.4.4 . end note

The definite-assignment states of instance variables of a struct_type variable are tracked individually as well as collectively. In additional to the rules described in §9.4.2 , §9.4.3 , and §9.4.4 , the following rules apply to struct_type variables and their instance variables:

• An instance variable is considered definitely assigned if its containing struct_type variable is considered definitely assigned.
• A struct_type variable is considered definitely assigned if each of its instance variables is considered definitely assigned.

Definite assignment is a requirement in the following contexts:

A variable shall be definitely assigned at each location where its value is obtained.

Note : This ensures that undefined values never occur. end note

The occurrence of a variable in an expression is considered to obtain the value of the variable, except when

• the variable is the left operand of a simple assignment,
• the variable is passed as an output parameter, or
• the variable is a struct_type variable and occurs as the left operand of a member access.

A variable shall be definitely assigned at each location where it is passed as a reference parameter.

Note : This ensures that the function member being invoked can consider the reference parameter initially assigned. end note

A variable shall be definitely assigned at each location where it is passed as an input parameter.

Note : This ensures that the function member being invoked can consider the input parameter initially assigned. end note

All output parameters of a function member shall be definitely assigned at each location where the function member returns (through a return statement or through execution reaching the end of the function member body).

Note : This ensures that function members do not return undefined values in output parameters, thus enabling the compiler to consider a function member invocation that takes a variable as an output parameter equivalent to an assignment to the variable. end note

The this variable of a struct_type instance constructor shall be definitely assigned at each location where that instance constructor returns.

9.4.2 Initially assigned variables

The following categories of variables are classified as initially assigned:

• Instance variables of initially assigned struct variables.
• Value parameters.
• Reference parameters.
• Input parameters.
• Variables declared in a catch clause or a foreach statement.

9.4.3 Initially unassigned variables

The following categories of variables are classified as initially unassigned:

• Instance variables of initially unassigned struct variables.
• Output parameters, including the this variable of struct instance constructors without a constructor initializer.
• Local variables, except those declared in a catch clause or a foreach statement.

9.4.4 Precise rules for determining definite assignment

9.4.4.1 general.

In order to determine that each used variable is definitely assigned, the compiler shall use a process that is equivalent to the one described in this subclause.

The compiler processes the body of each function member that has one or more initially unassigned variables. For each initially unassigned variable v , the compiler determines a definite-assignment state for v at each of the following points in the function member:

• At the beginning of each statement
• At the end point ( §13.2 ) of each statement
• On each arc which transfers control to another statement or to the end point of a statement
• At the beginning of each expression
• At the end of each expression

The definite-assignment state of v can be either:

• Definitely assigned. This indicates that on all possible control flows to this point, v has been assigned a value.
• Definitely assigned after true expression. This state indicates that v is definitely assigned if the Boolean expression evaluated as true, but is not necessarily assigned if the Boolean expression evaluated as false.
• Definitely assigned after false expression. This state indicates that v is definitely assigned if the Boolean expression evaluated as false, but is not necessarily assigned if the Boolean expression evaluated as true.

The following rules govern how the state of a variable v is determined at each location.

9.4.4.2 General rules for statements

• v is not definitely assigned at the beginning of a function member body.
• The definite-assignment state of v at the beginning of any other statement is determined by checking the definite-assignment state of v on all control flow transfers that target the beginning of that statement. If (and only if) v is definitely assigned on all such control flow transfers, then v is definitely assigned at the beginning of the statement. The set of possible control flow transfers is determined in the same way as for checking statement reachability ( §13.2 ).
• The definite-assignment state of v at the end point of a block , checked , unchecked , if , while , do , for , foreach , lock , using , or switch statement is determined by checking the definite-assignment state of v on all control flow transfers that target the end point of that statement. If v is definitely assigned on all such control flow transfers, then v is definitely assigned at the end point of the statement. Otherwise, v is not definitely assigned at the end point of the statement. The set of possible control flow transfers is determined in the same way as for checking statement reachability ( §13.2 ).

Note : Because there are no control paths to an unreachable statement, v is definitely assigned at the beginning of any unreachable statement. end note

9.4.4.3 Block statements, checked, and unchecked statements

The definite-assignment state of v on the control transfer to the first statement of the statement list in the block (or to the end point of the block, if the statement list is empty) is the same as the definite-assignment statement of v before the block, checked , or unchecked statement.

9.4.4.4 Expression statements

For an expression statement stmt that consists of the expression expr :

• v has the same definite-assignment state at the beginning of expr as at the beginning of stmt .
• If v if definitely assigned at the end of expr , it is definitely assigned at the end point of stmt ; otherwise, it is not definitely assigned at the end point of stmt .

9.4.4.5 Declaration statements

• If stmt is a declaration statement without initializers, then v has the same definite-assignment state at the end point of stmt as at the beginning of stmt .
• If stmt is a declaration statement with initializers, then the definite-assignment state for v is determined as if stmt were a statement list, with one assignment statement for each declaration with an initializer (in the order of declaration).

9.4.4.6 If statements

For a statement stmt of the form:

• If v is definitely assigned at the end of expr , then it is definitely assigned on the control flow transfer to then_stmt and to either else_stmt or to the end-point of stmt if there is no else clause.
• If v has the state “definitely assigned after true expression” at the end of expr , then it is definitely assigned on the control flow transfer to then_stmt , and not definitely assigned on the control flow transfer to either else_stmt or to the end-point of stmt if there is no else clause.
• If v has the state “definitely assigned after false expression” at the end of expr , then it is definitely assigned on the control flow transfer to else_stmt , and not definitely assigned on the control flow transfer to then_stmt . It is definitely assigned at the end-point of stmt if and only if it is definitely assigned at the end-point of then_stmt .
• Otherwise, v is considered not definitely assigned on the control flow transfer to either the then_stmt or else_stmt , or to the end-point of stmt if there is no else clause.

9.4.4.7 Switch statements

For a switch statement stmt with a controlling expression expr :

• The definite-assignment state of v at the beginning of expr is the same as the state of v at the beginning of stmt .

The definite-assignment state of v at the beginning of a case’s guard clause is

• If v is a pattern variable declared in the switch_label : “definitely assigned”.
• If the switch label containing that guard clause ( §13.8.3 ) is not reachable: “definitely assigned”.
• Otherwise, the state of v is the same as the state of v after expr .

Example : The second rule eliminates the need for the compiler to issue an error if an unassigned variable is accessed in unreachable code. The state of b is “definitely assigned” in the unreachable switch label case 2 when b . bool b; switch (1) { case 2 when b: // b is definitely assigned here. break; } end example

The definite-assignment state of v on the control flow transfer to a reachable switch block statement list is

• If the control transfer was due to a ‘goto case’ or ‘goto default’ statement, then the state of v is the same as the state at the beginning of that ‘goto’ statement.
• If the control transfer was due to the default label of the switch, then the state of v is the same as the state of v after expr .
• If the control transfer was due to an unreachable switch label, then the state of v is “definitely assigned”.
• If the control transfer was due to a reachable switch label with a guard clause, then the state of v is the same as the state of v after the guard clause.
• Otherwise, the state of v is the same as the stat of v after expr .

A consequence of these rules is that a pattern variable declared in a switch_label will be “not definitely assigned” in the statements of its switch section if it is not the only reachable switch label in its section.

Example : public static double ComputeArea(object shape) { switch (shape) { case Square s when s.Side == 0: case Circle c when c.Radius == 0: case Triangle t when t.Base == 0 || t.Height == 0: case Rectangle r when r.Length == 0 || r.Height == 0: // none of s, c, t, or r is definitely assigned return 0; case Square s: // s is definitely assigned return s.Side * s.Side; case Circle c: // c is definitely assigned return c.Radius * c.Radius * Math.PI; … } } end example

9.4.4.8 While statements

• If v is definitely assigned at the end of expr , then it is definitely assigned on the control flow transfer to while_body and to the end point of stmt .
• If v has the state “definitely assigned after true expression” at the end of expr , then it is definitely assigned on the control flow transfer to while_body , but not definitely assigned at the end-point of stmt .
• If v has the state “definitely assigned after false expression” at the end of expr , then it is definitely assigned on the control flow transfer to the end point of stmt , but not definitely assigned on the control flow transfer to while_body .

9.4.4.9 Do statements

• v has the same definite-assignment state on the control flow transfer from the beginning of stmt to do_body as at the beginning of stmt .
• v has the same definite-assignment state at the beginning of expr as at the end point of do_body .
• If v is definitely assigned at the end of expr , then it is definitely assigned on the control flow transfer to the end point of stmt .
• If v has the state “definitely assigned after false expression” at the end of expr , then it is definitely assigned on the control flow transfer to the end point of stmt , but not definitely assigned on the control flow transfer to do_body .

9.4.4.10 For statements

For a statement of the form:

definite-assignment checking is done as if the statement were written:

with continue statements that target the for statement being translated to goto statements targeting the label LLoop . If the for_condition is omitted from the for statement, then evaluation of definite-assignment proceeds as if for_condition were replaced with true in the above expansion.

9.4.4.11 Break, continue, and goto statements

The definite-assignment state of v on the control flow transfer caused by a break , continue , or goto statement is the same as the definite-assignment state of v at the beginning of the statement.

9.4.4.12 Throw statements

the definite-assignment state of v at the beginning of expr is the same as the definite-assignment state of v at the beginning of stmt .

9.4.4.13 Return statements

• The definite-assignment state of v at the beginning of expr is the same as the definite-assignment state of v at the beginning of stmt .
• or at the end of the finally block of a try - finally or try - catch - finally that encloses the return statement.
• before stmt

9.4.4.14 Try-catch statements

• The definite-assignment state of v at the beginning of try_block is the same as the definite-assignment state of v at the beginning of stmt .
• The definite-assignment state of v at the beginning of catch_block_i (for any i ) is the same as the definite-assignment state of v at the beginning of stmt .
• The definite-assignment state of v at the end-point of stmt is definitely assigned if (and only if) v is definitely assigned at the end-point of try_block and every catch_block_i (for every i from 1 to n ).

9.4.4.15 Try-finally statements

• The definite-assignment state of v at the beginning of finally_block is the same as the definite-assignment state of v at the beginning of stmt .
• v is definitely assigned at the end-point of try_block
• v is definitely assigned at the end-point of finally_block

If a control flow transfer (such as a goto statement) is made that begins within try_block , and ends outside of try_block , then v is also considered definitely assigned on that control flow transfer if v is definitely assigned at the end-point of finally_block . (This is not an only if—if v is definitely assigned for another reason on this control flow transfer, then it is still considered definitely assigned.)

9.4.4.16 Try-catch-finally statements

definite-assignment analysis is done as if the statement were a try - finally statement enclosing a try - catch statement:

Example : The following example demonstrates how the different blocks of a try statement ( §13.11 ) affect definite assignment. class A { static void F() { int i, j; try { goto LABEL; // neither i nor j definitely assigned i = 1; // i definitely assigned } catch { // neither i nor j definitely assigned i = 3; // i definitely assigned } finally { // neither i nor j definitely assigned j = 5; // j definitely assigned } // i and j definitely assigned LABEL: ; // j definitely assigned } } end example

9.4.4.17 Foreach statements

• The definite-assignment state of v on the control flow transfer to embedded_statement or to the end point of stmt is the same as the state of v at the end of expr .

9.4.4.18 Using statements

• The definite-assignment state of v at the beginning of resource_acquisition is the same as the state of v at the beginning of stmt .
• The definite-assignment state of v on the control flow transfer to embedded_statement is the same as the state of v at the end of resource_acquisition .

9.4.4.19 Lock statements

• The definite-assignment state of v on the control flow transfer to embedded_statement is the same as the state of v at the end of expr .

9.4.4.20 Yield statements

• The definite-assignment state of v at the end of stmt is the same as the state of v at the end of expr .

A yield break statement has no effect on the definite-assignment state.

9.4.4.21 General rules for constant expressions

The following applies to any constant expression, and takes priority over any rules from the following sections that might apply:

For a constant expression with value true :

• If v is definitely assigned before the expression, then v is definitely assigned after the expression.
• Otherwise v is “definitely assigned after false expression” after the expression.

Example : int x; if (true) {} else { Console.WriteLine(x); } end example

For a constant expression with value false :

• Otherwise v is “definitely assigned after true expression” after the expression.

Example : int x; if (false) { Console.WriteLine(x); } end example

For all other constant expressions, the definite-assignment state of v after the expression is the same as the definite-assignment state of v before the expression.

9.4.4.22 General rules for simple expressions

The following rule applies to these kinds of expressions: literals ( §12.8.2 ), simple names ( §12.8.4 ), member access expressions ( §12.8.7 ), non-indexed base access expressions ( §12.8.14 ), typeof expressions ( §12.8.17 ), default value expressions ( §12.8.20 ), nameof expressions ( §12.8.22 ), and declaration expressions ( §12.17 ).

• The definite-assignment state of v at the end of such an expression is the same as the definite-assignment state of v at the beginning of the expression.

9.4.4.23 General rules for expressions with embedded expressions

The following rules apply to these kinds of expressions: parenthesized expressions ( §12.8.5 ), tuple expressions ( §12.8.6 ), element access expressions ( §12.8.11 ), base access expressions with indexing ( §12.8.14 ), increment and decrement expressions ( §12.8.15 , §12.9.6 ), cast expressions ( §12.9.7 ), unary + , - , ~ , * expressions, binary + , - , * , / , % , << , >> , < , <= , > , >= , == , != , is , as , & , | , ^ expressions ( §12.10 , §12.11 , §12.12 , §12.13 ), compound assignment expressions ( §12.21.4 ), checked and unchecked expressions ( §12.8.19 ), array and delegate creation expressions ( §12.8.16 ) , and await expressions ( §12.9.8 ).

Each of these expressions has one or more subexpressions that are unconditionally evaluated in a fixed order.

Example : The binary % operator evaluates the left hand side of the operator, then the right hand side. An indexing operation evaluates the indexed expression, and then evaluates each of the index expressions, in order from left to right. end example

For an expression expr , which has subexpressions expr₁ , expr₂ , …, exprₓ , evaluated in that order:

• The definite-assignment state of v at the beginning of expr₁ is the same as the definite-assignment state at the beginning of expr .
• The definite-assignment state of v at the beginning of exprᵢ ( i greater than one) is the same as the definite-assignment state at the end of exprᵢ₋₁ .
• The definite-assignment state of v at the end of expr is the same as the definite-assignment state at the end of exprₓ .

9.4.4.24 Invocation expressions and object creation expressions

If the method to be invoked is a partial method that has no implementing partial method declaration, or is a conditional method for which the call is omitted ( §22.5.3.2 ), then the definite-assignment state of v after the invocation is the same as the definite-assignment state of v before the invocation. Otherwise the following rules apply:

For an invocation expression expr of the form:

or an object-creation expression expr of the form:

• For an invocation expression, the definite assignment state of v before primary_expression is the same as the state of v before expr .
• For an invocation expression, the definite assignment state of v before arg₁ is the same as the state of v after primary_expression .
• For an object creation expression, the definite assignment state of v before arg₁ is the same as the state of v before expr .
• For each argument argᵢ , the definite assignment state of v after argᵢ is determined by the normal expression rules, ignoring any in , out , or ref modifiers.
• For each argument argᵢ for any i greater than one, the definite assignment state of v before argᵢ is the same as the state of v after argᵢ₋₁ .
• If the variable v is passed as an out argument (i.e., an argument of the form “out v ”) in any of the arguments, then the state of v after expr is definitely assigned. Otherwise, the state of v after expr is the same as the state of v after argₓ .
• For array initializers ( §12.8.16.5 ), object initializers ( §12.8.16.3 ), collection initializers ( §12.8.16.4 ) and anonymous object initializers ( §12.8.16.7 ), the definite-assignment state is determined by the expansion that these constructs are defined in terms of.

9.4.4.25 Simple assignment expressions

Let the set of assignment targets in an expression e be defined as follows:

• If e is a tuple expression, then the assignment targets in e are the union of the assignment targets of the elements of e .
• Otherwise, the assignment targets in e are e .

For an expression expr of the form:

• The definite-assignment state of v before expr_lhs is the same as the definite-assignment state of v before expr .
• The definite-assignment state of v before expr_rhs is the same as the definite-assignment state of v after expr_lhs .
• If v is an assignment target of expr_lhs , then the definite-assignment state of v after expr is definitely assigned. Otherwise, if the assignment occurs within the instance constructor of a struct type, and v is the hidden backing field of an automatically implemented property P on the instance being constructed, and a property access designating P is an assigment target of expr_lhs , then the definite-assignment state of v after expr is definitely assigned. Otherwise, the definite-assignment state of v after expr is the same as the definite-assignment state of v after expr_rhs .

Example : In the following code class A { static void F(int[] arr) { int x; arr[x = 1] = x; // ok } } the variable x is considered definitely assigned after arr[x = 1] is evaluated as the left hand side of the second simple assignment. end example

9.4.4.26 && expressions

• The definite-assignment state of v before expr_first is the same as the definite-assignment state of v before expr .
• The definite-assignment state of v before expr_second is definitely assigned if and only if the state of v after expr_first is either definitely assigned or “definitely assigned after true expression”. Otherwise, it is not definitely assigned.
• If the state of v after expr_first is definitely assigned, then the state of v after expr is definitely assigned.
• Otherwise, if the state of v after expr_second is definitely assigned, and the state of v after expr_first is “definitely assigned after false expression”, then the state of v after expr is definitely assigned.
• Otherwise, if the state of v after expr_second is definitely assigned or “definitely assigned after true expression”, then the state of v after expr is “definitely assigned after true expression”.
• Otherwise, if the state of v after expr_first is “definitely assigned after false expression”, and the state of v after expr_second is “definitely assigned after false expression”, then the state of v after expr is “definitely assigned after false expression”.
• Otherwise, the state of v after expr is not definitely assigned.

Example : In the following code class A { static void F(int x, int y) { int i; if (x >= 0 && (i = y) >= 0) { // i definitely assigned } else { // i not definitely assigned } // i not definitely assigned } } the variable i is considered definitely assigned in one of the embedded statements of an if statement but not in the other. In the if statement in method F , the variable i is definitely assigned in the first embedded statement because execution of the expression (i = y) always precedes execution of this embedded statement. In contrast, the variable i is not definitely assigned in the second embedded statement, since x >= 0 might have tested false, resulting in the variable i ’s being unassigned. end example

9.4.4.27 || expressions

• Otherwise, if the state of v after expr_second is definitely assigned, and the state of v after expr_first is “definitely assigned after true expression”, then the state of v after expr is definitely assigned.
• Otherwise, if the state of v after expr_second is definitely assigned or “definitely assigned after false expression”, then the state of v after expr is “definitely assigned after false expression”.
• Otherwise, if the state of v after expr_first is “definitely assigned after true expression”, and the state of v after expr_ second is “definitely assigned after true expression”, then the state of v after expr is “definitely assigned after true expression”.

Example : In the following code class A { static void G(int x, int y) { int i; if (x >= 0 || (i = y) >= 0) { // i not definitely assigned } else { // i definitely assigned } // i not definitely assigned } } the variable i is considered definitely assigned in one of the embedded statements of an if statement but not in the other. In the if statement in method G , the variable i is definitely assigned in the second embedded statement because execution of the expression (i = y) always precedes execution of this embedded statement. In contrast, the variable i is not definitely assigned in the first embedded statement, since x >= 0 might have tested true, resulting in the variable i ’s being unassigned. end example

9.4.4.28 ! expressions

• The definite-assignment state of v before expr_operand is the same as the definite-assignment state of v before expr .
• If the state of v after expr_operand is definitely assigned, then the state of v after expr is definitely assigned.
• Otherwise, if the state of v after expr_operand is “definitely assigned after false expression”, then the state of v after expr is “definitely assigned after true expression”.
• Otherwise, if the state of v after expr_operand is “definitely assigned after true expression”, then the state of v after expr is “definitely assigned after false expression”.

9.4.4.29 ?? expressions

• The definite-assignment state of v before expr_second is the same as the definite-assignment state of v after expr_first .
• If expr_first is a constant expression ( §12.23 ) with value null , then the state of v after expr is the same as the state of v after expr_second .
• Otherwise, the state of v after expr is the same as the definite-assignment state of v after expr_first .

9.4.4.30 ?: expressions

• The definite-assignment state of v before expr_cond is the same as the state of v before expr .
• The definite-assignment state of v before expr_true is definitely assigned if the state of v after expr_cond is definitely assigned or “definitely assigned after true expression”.
• The definite-assignment state of v before expr_false is definitely assigned if the state of v after expr_cond is definitely assigned or “definitely assigned after false expression”.
• If expr_cond is a constant expression ( §12.23 ) with value true then the state of v after expr is the same as the state of v after expr_true .
• Otherwise, if expr_cond is a constant expression ( §12.23 ) with value false then the state of v after expr is the same as the state of v after expr_false .
• Otherwise, if the state of v after expr_true is definitely assigned and the state of v after expr_false is definitely assigned, then the state of v after expr is definitely assigned.

9.4.4.31 Anonymous functions

For a lambda_expression or anonymous_method_expression expr with a body (either block or expression ) body :

• The definite assignment state of a parameter is the same as for a parameter of a named method ( §9.2.6 , §9.2.7 , §9.2.8 ).
• The definite assignment state of an outer variable v before body is the same as the state of v before expr . That is, definite assignment state of outer variables is inherited from the context of the anonymous function.
• The definite assignment state of an outer variable v after expr is the same as the state of v before expr .

Example : The example class A { delegate bool Filter(int i); void F() { int max; // Error, max is not definitely assigned Filter f = (int n) => n < max; max = 5; DoWork(f); } void DoWork(Filter f) { ... } } generates a compile-time error since max is not definitely assigned where the anonymous function is declared. end example

Example : The example class A { delegate void D(); void F() { int n; D d = () => { n = 1; }; d(); // Error, n is not definitely assigned Console.WriteLine(n); } } also generates a compile-time error since the assignment to n in the anonymous function has no affect on the definite-assignment state of n outside the anonymous function. end example

9.4.4.32 Throw expressions

throw thrown_expr

• The definite assignment state of v before thrown_expr is the same as the state of v before expr .
• The definite assignment state of v after expr is “definitely assigned”.

9.4.4.33 Rules for variables in local functions

Local functions are analyzed in the context of their parent method. There are two control flow paths that matter for local functions: function calls and delegate conversions.

Definite assignment for the body of each local function is defined separately for each call site. At each invocation, variables captured by the local function are considered definitely assigned if they were definitely assigned at the point of call. A control flow path also exists to the local function body at this point and is considered reachable. After a call to the local function, captured variables that were definitely assigned at every control point leaving the function ( return statements, yield statements, await expressions) are considered definitely assigned after the call location.

Delegate conversions have a control flow path to the local function body. Captured variables are definitely assigned for the body if they are definitely assigned before the conversion. Variables assigned by the local function are not considered assigned after the conversion.

Note : the above implies that bodies are re-analyzed for definite assignment at every local function invocation or delegate conversion. Compilers are not required to re-analyze the body of a local function at each invocation or delegate conversion. The implementation must produce results equivalent to that description. end note

Example : The following example demonstrates definite assignment for captured variables in local functions. If a local function reads a captured variable before writing it, the captured variable must be definitely assigned before calling the local function. The local function F1 reads s without assigning it. It is an error if F1 is called before s is definitely assigned. F2 assigns i before reading it. It may be called before i is definitely assigned. Furthermore, F3 may be called after F2 because s2 is definitely assigned in F2 . void M() { string s; int i; string s2; // Error: Use of unassigned local variable s: F1(); // OK, F2 assigns i before reading it. F2(); // OK, i is definitely assigned in the body of F2: s = i.ToString(); // OK. s is now definitely assigned. F1(); // OK, F3 reads s2, which is definitely assigned in F2. F3(); void F1() { Console.WriteLine(s); } void F2() { i = 5; // OK. i is definitely assigned. Console.WriteLine(i); s2 = i.ToString(); } void F3() { Console.WriteLine(s2); } } end example

9.4.4.34 is-pattern expressions

expr_operand is pattern

• If the variable ‘v’ is declared in pattern , then the definite-assignment state of ‘v’ after expr is “definitely assigned when true”.
• Otherwise the definite assignment state of ‘v’ after expr is the same as the definite assignment state of ‘v’ after expr_operand .

9.5 Variable references

A variable_reference is an expression that is classified as a variable. A variable_reference denotes a storage location that can be accessed both to fetch the current value and to store a new value.

Note : In C and C++, a variable_reference is known as an lvalue . end note

9.6 Atomicity of variable references

Reads and writes of the following data types shall be atomic: bool , char , byte , sbyte , short , ushort , uint , int , float , and reference types. In addition, reads and writes of enum types with an underlying type in the previous list shall also be atomic. Reads and writes of other types, including long , ulong , double , and decimal , as well as user-defined types, need not be atomic. Aside from the library functions designed for that purpose, there is no guarantee of atomic read-modify-write, such as in the case of increment or decrement.

9.7 Reference variables and returns

9.7.1 general.

A reference variable is a variable that refers to another variable, called the referent ( §9.2.6 ). A reference variable is a local variable declared with the ref modifier.

A reference variable stores a variable_reference ( §9.5 ) to its referent and not the value of its referent. When a reference variable is used where a value is required its referent’s value is returned; similarly when a reference variable is the target of an assignment it is the referent which is assigned to. The variable to which a reference variable refers, i.e. the stored variable_reference for its referent, can be changed using a ref assignment ( = ref ).

Example: The following example demonstrates a local reference variable whose referent is an element of an array: public class C { public void M() { int[] arr = new int[10]; // element is a reference variable that refers to arr[5] ref int element = ref arr[5]; element += 5; // arr[5] has been incremented by 5 } } end example

A reference return is the variable_reference returned from a returns-by-ref method ( §15.6.1 ). This variable_reference is the referent of the reference return.

Example: The following example demonstrates a reference return whose referent is an element of an array field: public class C { private int[] arr = new int[10]; public ref readonly int M() { // element is a reference variable that refers to arr[5] ref int element = ref arr[5]; return ref element; // return reference to arr[5]; } } end example

9.7.2 Ref safe contexts

9.7.2.1 general.

All reference variables obey safety rules that ensure the ref-safe-context of the reference variable is not greater than the ref-safe-context of its referent.

Note : The related notion of a safe-context is defined in ( §16.4.12 ), along with associated constraints. end note

For any variable, the ref-safe-context of that variable is the context where a variable_reference ( §9.5 ) to that variable is valid. The referent of a reference variable shall have a ref-safe-context that is at least as wide as the ref-safe-context of the reference variable itself.

Note : The compiler determines the ref-safe-context through a static analysis of the program text. The ref-safe-context reflects the lifetime of a variable at runtime. end note

There are three ref-safe-contexts:

declaration-block : The ref-safe-context of a variable_reference to a local variable ( §9.2.9 ) is that local variable’s scope ( §13.6.2 ), including any nested embedded-statement s in that scope.

A variable_reference to a local variable is a valid referent for a reference variable only if the reference variable is declared within the ref-safe-context of that variable.

function-member : Within a function a variable_reference to any of the following has a ref-safe-context of function-member:

• Value parameters ( §9.2.5 ) on a function member declaration, including the implicit this of class member functions; and
• The implicit reference ( ref ) parameter ( §9.2.6 ) this of a struct member function, along with its fields.

A variable_reference with ref-safe-context of function-member is a valid referent only if the reference variable is declared in the same function member.

caller-context : Within a function a variable_reference to any of the following has a ref-safe-context of caller-context:

• Reference ( ref ) parameters ( §9.2.6 ) other than the implicit this of a struct member function;
• Member fields and elements of such parameters;
• Member fields of parameters of class type; and
• Elements of parameters of array type.

A variable_reference with ref-safe-context of caller-context can be the referent of a reference return.

These values form a nesting relationship from narrowest (declaration-block) to widest (caller-context). Each nested block represents a different context.

Example : The following code shows examples of the different ref-safe-contexts. The declarations show the ref-safe-context for a referent to be the initializing expression for a ref variable. The examples show the ref-safe-context for a reference return: public class C { // ref safe context of arr is "caller-context". // ref safe context of arr[i] is "caller-context". private int[] arr = { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 }; // ref safe context is "caller-context" public ref int M1(ref int r1) { return ref r1; // r1 is safe to ref return } // ref safe context is "function-member" public ref int M2(int v1) { return ref v1; // error: v1 isn't safe to ref return } public ref int M3() { int v2 = 5; return ref arr[v2]; // arr[v2] is safe to ref return } public void M4(int p) { int v3 = 6; // context of r2 is declaration-block, // ref safe context of p is function-member ref int r2 = ref p; // context of r3 is declaration-block, // ref safe context of v3 is declaration-block ref int r3 = ref v3; // context of r4 is declaration-block, // ref safe context of arr[v3] is caller-context ref int r4 = ref arr[v3]; } } end example.

Example : For struct types, the implicit this parameter is passed as a ref parameter. The ref-safe-context of the fields of a struct type as function-member prevents returning those fields by reference return. This rule prevents the following code: public struct S { private int n; // Disallowed: returning ref of a field. public ref int GetN() => ref n; } class Test { public ref int M() { S s = new S(); ref int numRef = ref s.GetN(); return ref numRef; // reference to local variable 'numRef' returned } } end example.

9.7.2.2 Local variable ref safe context

For a local variable v :

• If v is a reference variable, its ref-safe-context is the same as the ref-safe-context of its initializing expression.
• Otherwise its ref-safe-context is declaration-block.

9.7.2.3 Parameter ref safe context

For a formal parameter p :

• If p is a ref , or in parameter, its ref-safe-context is the caller-context. If p is an in parameter, it can’t be returned as a writable ref but can be returned as ref readonly .
• If p is an out parameter, its ref-safe-context is the caller-context.
• Otherwise, if p is the this parameter of a struct type, its ref-safe-context is the function-member.
• Otherwise, the parameter is a value parameter, and its ref-safe-context is the function-member.

9.7.2.4 Field ref safe context

For a variable designating a reference to a field, e.F :

• If e is of a reference type, its ref-safe-context is the caller-context.
• Otherwise, if e is of a value type, its ref-safe-context is the same as the ref-safe-context of e .

9.7.2.5 Operators

The conditional operator ( §12.18 ), c ? ref e1 : ref e2 , and reference assignment operator, = ref e ( §12.21.1 ) have reference variables as operands and yield a reference variable. For those operators, the ref-safe-context of the result is the narrowest context among the ref-safe-contexts of all ref operands.

9.7.2.6 Function invocation

For a variable c resulting from a ref-returning function invocation, its ref-safe-context is the narrowest of the following contexts:

• The caller-context.
• The ref-safe-context of all ref , out , and in argument expressions (excluding the receiver).
• For each in parameter, if there is a corresponding expression that is a variable and there exists an identity conversion between the type of the variable and the type of the parameter, the variable’s ref-safe-context, otherwise the nearest enclosing context.
• The safe-context ( §16.4.12 ) of all argument expressions (including the receiver).

Example : the last bullet is necessary to handle code such as ref int M2() { int v = 5; // Not valid. // ref safe context of "v" is block. // Therefore, ref safe context of the return value of M() is block. return ref M(ref v); } ref int M(ref int p) { return ref p; } end example

A property invocation and an indexer invocation (either get or set ) is treated as a function invocation of the underlying accessor by the above rules. A local function invocation is a function invocation.

9.7.2.7 Values

A value’s ref-safe-context is the nearest enclosing context.

Note : This occurs in an invocation such as M(ref d.Length) where d is of type dynamic . It is also consistent with arguments corresponding to in parameters. end note

9.7.2.8 Constructor invocations

A new expression that invokes a constructor obeys the same rules as a method invocation ( §9.7.2.6 ) that is considered to return the type being constructed.

9.7.2.9 Limitations on reference variables

• Neither a reference parameter, nor an output parameter, nor an input parameter, nor a ref local, nor a parameter or local of a ref struct type shall be captured by lambda expression or local function.
• Neither a reference parameter, nor an output parameter, nor an input parameter, nor a parameter of a ref struct type shall be an argument for an iterator method or an async method.
• Neither a ref local, nor a local of a ref struct type shall be in context at the point of a yield return statement or an await expression.
• For a ref reassignment e1 = ref e2 , the ref-safe-context of e2 shall be at least as wide a context as the ref-safe-context of e1 .
• For a ref return statement return ref e1 , the ref-safe-context of e1 shall be the caller-context.

ECMA C# draft specification

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TypeScript definite assignment assertions

TypeScript never stops improving, although most changes over the past year have been “non syntactical” – i.e. there have been a huge swathe of improvements to how types are handled, and a large slice of improvements to make the tooling even better. It has a been a while, though, since we got a new character to decorate our code. The wait is over, thanks to the TypeScript Definite Assignment Assertion. Let’s take a look at it with a short example.

No definite assignment

The new feature is related to the following improved compile-time check. In the example below, I forgot to assign a value to the wordsPerMinute property. This can happen when you forget to add a default value, or when you forget to initialize it in the constructor, or (as below) when you forget to map a parameter to the property (remember, you don’t need to manually map constructor parameters !).

Whatever the reason, if you compile using the strict flag (I keep telling you to use it), you’ll get the following error, known as a definite assignment error because there is no definite assignment:

app.ts(2,13): error TS2564: Property ‘wordsPerMinute’ has no initializer and is not definitely assigned in the constructor.

Fixing, and definite assignment assertions

The correct fix is probably to assign this.wordsPerMinute = wordsPerMinute in the constructor – but in some cases, you may be doing something funky where the dependency will be resolved in a way the compiler is unable to determine.

When you need to allow a property with no definite assignment, you can use the definite assignment assertion . This is a very grand name for adding a bang (!) to the property name.

This will only work in TypeScript 2.7 and newer.

On the whole, unless you have an iron-clad reason to use it – you’ll probably want to avoid the definite assignment assertion. In most cases, the real value of this feature lies in the part that detects unassigned properties.

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Definite Assignment Analysis of locals. The real purpose.

7 minute read

Definite Assignment Analysis prevents bugs, but there are deeper reasons to have it as a required feature in the language.

Indeed - Why have such strict rules instead of just assuming that unassigned locals contain default/zero values? After all, that seems to work ok for fields. It is also known that C# compiler decorates all methods with IL directive localsinit , which guarantees that all locals are zeroed out when method is entered. So what is the problem?

localsinit is, unfortunately, not enough to implement the semantics of C# locals. It would work if the life time of all local bindings (i.e. extents ), was the whole method, but that is not the case in C#. In C# locals can have scopes smaller than the entirety of a method and extents match the lexical scopes. Every time the control flow enters a scope, a new set of bindings for the locals contained by that scope is supposed to be created and the bindings exist as long as they can be referenced. In the most general sense the “new bindings” would imply a newly allocated storage completely unrelated to the bindings possibly created when the same scope was entered previously.

A brute-force solution would be to map local variables of the same scope to fields in a synthesized class and create a new instance of such class when entering a scope. In fact this is what happens to locals that are accessible from lambda expressions. Such locals can be used beyond the life time of the containing method and multiple bindings to the same variables could coexist at the same time, so compiler needs to allocate their storage on the heap and rely on GC for keeping them alive as long as they can be referenced.

Example of multiple bindings to the same local:

The most common case is, however, when locals are just that - locals. They are not accessed from lambdas or anything like that and at any time only one (or none) bindings to such local may exist. In such cases locals can be simply mapped to IL local slots and reused every time the control flow enters the scope. The only problem is that the slot values would need to be “reset” every time the scope is entered to the default value and there is no help from localsinit here since that works only once - when the whole method is invoked.

In theory, compiler could inject code that would do the “resetting” of all relevant slots, when a scope is entered, but that would be wasteful. Only some of the locals in a given scope would be read from. Besides, most of them would be written to before reading anyways, so why not just require that a local is written to before being read? That would make the code less buggy, but most of all it will make the “resetting” entirely unnecessary.

Essentially, a rule that requires that locals are definitely assigned before being read serves the same purpose as localsinit , but does much better job.

• It works at every nested lexical scope recursively (not just on the method level)
• It gives stronger guarantees. You can see only what you have already assigned to the variable. It is impossible to read uninitialized/stale state by accident.
• It is minimally redundant. If you do not read a local on some code path you do not need to ensure that it is assigned on that code path

Simple example of some variables assigned on one code path and not assigned on the other. As long as we do not read the variable it is ok to have it not assigned.

Interestingly, in VB, for historical reasons, locals not referenced from lambdas do have extents that match the entirety of the method and thus definite assignment analysis is much less strict - it basically exists just to give warnings on some cases that likely to be coding mistakes.

example of a VB local binding maintained through the entirety of the method life time:

The locals captured into lambda closures, however, have scoped extents in VB - surely the lifetimes cannot be bound to the lifetime of the containing method anymore when lambdas are involved. Similarly to C#, fresh bindings for captured locals are created when scope is entered and their lifetimes are bound to the lifetime of the referencing lambdas. So if locals are captured, the example above would start behaving differently. To make the unfortunate inconsistency less observable, VB refuses to compile code like above when locals are captured.

Pedantic observations:

Since C# enforces stronger invariant than provided by localsinit , one would wonder why compiler still puts localsinit on methods. A simple answer is that IL verification rules require that. The underlying reason for the requirement is that the user’s code is not the only entity that might read the locals. The other one is the Garbage Collector.

The issue with GC is that it scans the IL locals of currently active methods in order to record the roots of reachable object graphs, and GC happens at fairly random times. Definite assignment analysis does not guarantee that locals will be assigned something deterministic before GC happens and things will go terribly bad if locals contain random junk. Therefore there is a rule that requires that verifiable methods have localsinit as an instruction directing the JIT to add a method preamble that wipes the whole stack frame clean before the method body is formally entered and GC had any chance to scan the locals.

In theory the rule could be required only on methods with locals of reference types (or structs containing references), but that would make a difference only to a fraction of methods while complicating the rule. Instead CLI standard allows JIT implementations to disregard the directive if, through some analysis, it could be inferred that not wiping the frame is a safe thing to do.

I am not sure if JITs use this kink in the rules very often though. With exception of the most trivial cases, the analysis could be too involved to be feasible at JIT time and wiping the stack frame is not overly expensive. Still, since there are some costs associated with locals (wiping the frame is just one of them), C# compiler generally tries to be frugal with usage of local slots, especially when compiling with /o+.

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Definite Assignment

C# requires definite assignment ; that is, variables must be initialized (or assigned to) before they are used. To test this rule, change the line that initializes myInt in Example 5-1 to:

and save the revised program shown in Example 5-2 .

Example 5-2. Uninitialized variable

When you try to compile Example 5-2 , the C# compiler will display the following error message:

It is not legal to use an uninitialized variable in C#; doing so violates the rule of definite assignment. In this case, “using” the variable myInt means passing it to WriteLine( ).

So does this mean you must initialize every variable? No, but if you don’t initialize your variable then you must assign a value to it before you attempt to use it. Example 5-3 illustrates a corrected program.

Example 5-3. Definite assignment

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/əˈsaɪnmənt/.

Other forms: assignments

Whether you’re an international spy with a new mission or a high school student with math homework — when you get an assignment , you’d better do it! An assignment is a task that someone in authority has asked you to do.

The word assignment is just the noun form of the common verb assign , which you use when you want to give someone a duty or a job. When you assign something, that something is called an assignment . The word can also refer to the act of distributing something. If you are distributing new office furniture at work, you might say, “ Assignment of the new chairs will begin tomorrow.”

• noun an undertaking that you have been assigned to do (as by an instructor) see more see less types: show 6 types... hide 6 types... school assignment , schoolwork a school task performed by a student to satisfy the teacher writing assignment , written assignment an assignment to write something classroom project a school task requiring considerable effort classwork the part of a student's work that is done in the classroom homework , prep , preparation preparatory school work done outside school (especially at home) lesson a task assigned for individual study type of: labor , project , task , undertaking any piece of work that is undertaken or attempted
• noun a duty that you are assigned to perform (especially in the armed forces) “a hazardous assignment ” synonyms: duty assignment see more see less types: show 10 types... hide 10 types... guard , guard duty , sentry duty , sentry go the duty of serving as a sentry fatigue , fatigue duty labor of a nonmilitary kind done by soldiers (cleaning or digging or draining or so on) charge , commission , mission a special assignment that is given to a person or group reassignment assignment to a different duty sea-duty , service abroad , shipboard duty naval service aboard a ship at sea shore duty naval service at land bases fool's errand a fruitless mission mission impossible an extremely dangerous or difficult mission martyr operation , sacrifice operation , suicide mission killing or injuring others while annihilating yourself; usually accomplished with a bomb secondment the detachment of a person from their regular organization for temporary assignment elsewhere type of: duty work that you are obliged to perform for moral or legal reasons
• noun the act of putting a person into a non-elective position synonyms: appointment , designation , naming see more see less types: show 6 types... hide 6 types... nomination the act of officially naming a candidate co-optation , co-option the act of appointing summarily (with or without the appointee's consent) delegacy the appointment of a delegate ordinance , ordination the act of ordaining; the act of conferring (or receiving) holy orders recognition designation by the chair granting a person the right to speak in a deliberative body laying on of hands laying hands on a person's head to invoke spiritual blessing in Christian ordination type of: conclusion , decision , determination the act of making up your mind about something
• noun the act of distributing something to designated places or persons “the first task is the assignment of an address to each datum” synonyms: assigning see more see less types: allocation , storage allocation (computer science) the assignment of particular areas of a magnetic disk to particular data or instructions type of: distribution the act of distributing or spreading or apportioning
• noun (law) a transfer of property by deed of conveyance synonyms: grant see more see less types: apanage , appanage a grant (by a sovereign or a legislative body) of resources to maintain a dependent member of a ruling family land grant a grant of public land (as to a railway or college) type of: transferred possession , transferred property a possession whose ownership changes or lapses
• noun the instrument by which a claim or right or interest or property is transferred from one person to another see more see less type of: instrument , legal document , legal instrument , official document (law) a document that states some contractual relationship or grants some right

Vocabulary lists containing assignment

The Dawes Act, or General Allotment Act of 1887, was a law that allowed the U.S. government to take Native American tribal lands and divide them into 40 acre lots for individual Native Americans. The goal was to break up communal tribal lands and speed the assimilation of Native Americans into American society. The Dawes Act caused great suffering with much of the land winding up in the hands of white settlers.

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Meaning of assignment in English

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• It was a plum assignment - more of a vacation really.
• He took this award-winning photograph while on assignment in the Middle East .
• His two-year assignment to the Mexico office starts in September .
• She first visited Norway on assignment for the winter Olympics ten years ago.
• He fell in love with the area after being there on assignment for National Geographic in the 1950s.
• act as something
• all work and no play (makes Jack a dull boy) idiom
• be at work idiom
• be in work idiom
• housekeeping
• in the line of duty idiom
• join duty idiom
• undertaking

You can also find related words, phrases, and synonyms in the topics:

assignment | Intermediate English

Assignment | business english, examples of assignment, collocations with assignment.

These are words often used in combination with assignment .

Click on a collocation to see more examples of it.

Translations of assignment

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the moon when it is shaped like a crescent, or a time when it is shaped like this

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Assignments

• by teachmint@wp

What is assignment in education? Assignment meaning is the tasks given to students by their teachers and tutors to complete in a defined time. They can also be referred to as the work given to someone as a part of learning. Assignments can be in the form of written, practical, art or fieldwork, or even online. Their purpose is to ensure that students understand the subject matter thoroughly.

Generally, students are assigned a task as a part of their homework. The allocation of assignments is not only restricted to a class or subject but this method can be applied at any stage of life. They are a great way to judge the ability and understanding of an individual towards a subject matter.

The culture of providing homework starts from kindergarten in various forms. Small children are asked to read and write what they learn in the class. Students in the higher class are given work as a part of their revision exercise and help them prepare for exams. Individuals doing honors write journals as a part of an assignment that determines their knowledge in that subject.

The structure of assignments depends upon the nature of the task and subject. They must be well-researched, including case studies or examples within a proper framework. These studies are useful for students to achieve the desired examination results. It also helps them to concentrate better on education. Knowing what is assignment in education helps teachers assess students better.

Importance of Assignments

Giving assignments to the students is a crucial part of student assessment. The importance of giving assignments to the students is discussed in detail below:

• Learning practical skills Assignments enable students to develop new skills. In order to complete the assignments, students learn new skills which help them in their academic careers. 
• Enhances time management skills Whenever assignments are allocated to the students, a time limit is set by teachers within which the assignment has to be submitted. What is assignment in education enable students to complete their tasks and learn timely submission of work. 
• Learning researching skills Students tend to do a lot of research about the questions given in the assignment. Assignment meaning is to help them develop their research skills and come in handy in their future careers. 
• Enhance the Writing Caliber Many students have a problem of not being able to put their thoughts into words. Writing assignments can help them develop writing skills and be expressive in real life as well. 

Since assignments are deadline-based, they help students take responsibility and manage time. The work assigned to students may be individual or group activities, or both, to develop teamwork in them. 

The above-mentioned information gives us a context of assignment meaning and its importance to the students. Assignments provide a basis for the student assessment and should be given timely.  

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• Using Manufacturing

How You Create an Assemble to Order (ATO) Model Work Definition

Oracle Fusion Cloud Manufacturing supports configured item fulfillment flow for a make-to-order configured product. The customer order is created with the Assemble to Order (ATO) model as the ordered item. When an ATO model is ordered, the customer has the ability to configure the model and select the options. The selected options result in a configuration and for each unique configuration, the application creates a configured item. Then, the work order to fulfill the customer order is created against the configured item.

To create a work order for a configured item, a primary work definition for the ATO model must be defined first. There are a few traits about an ATO model work definition that are different from a standard item work definition. The specifics are highlighted and discussed here in more detail.

ATO Model Work Definition Operations

In an ATO model work definition, the Create Operation, Assign Operation, and Edit Operation dialog boxes display the Option Dependent Details region.

The following table lists all the fields and their corresponding descriptions which helps you to choose or select values in order to create an ATO model work definition:

ATO Model Work Definition Operation Items

You can create an ATO model work definition only for the ATO model item structure with the structure name as Primary. The item structure visualization displays the multilevel ATO model item structure. You can expand option classes to view the options. You can also expand standard item phantoms to view the components that make up the phantoms. However, you can't expand child ATO models.

The count badge that you see against an item structure component card indicates the number of components for a single parent node. The count badge, shown only for a leaf node, indicates the assigned quantity over the component total quantity. The count badge turns into a check mark after the component is assigned to an operation. If you hover over the check mark icon, you can view the operation sequence to which the component is assigned to.

You can assign any component from any level to an operation. The rules governing this feature:

If the parent is assigned, the children can't be assigned.

If the children are assigned, assigning the parent automatically deletes the children's assignments.

This means for an option class, you can choose whether to assign the option class or the options. Similarly for a standard item phantom, you can choose whether to assign the parent phantom or the components. Assigning an option class to an option-dependent operation means that the operation is included in the configured item work order if any of the options of the specific option class is selected.

There are two operation item attributes that are specific to ATO model work definitions. These attributes are referenced from Oracle Product Hub and hence, can't be updated. The operation item attributes specific to ATO model work definitions are:

Planning Percentage: The percentage that's used by Planning in forecast explosions. A planning percent can be greater than 100 to plan for a component in excess.

Optional: Indicator that a component is an optional component. If the Optional check box isn't selected, then the component is considered as a mandatory component.

For more information, refer to the How You Process Item Structure Changes to Work Definitions topic in this chapter.

Applicability Rule

An applicability rule can be assigned to an option dependent operation. The rule defines the criteria to include the operation in the configured item work order. The operation is included in the work order only if the criteria are met. You can define an applicability rule using optional components, option classes, transactional item attributes (TIA), or any of the combinations.

Consider an example, in which, there are two types of performance tests as a part of building tablets. Depending on the selected CPU option, one of the performance test operation is executed. You can model this by doing the following:

Create two option dependent operations for the two types of performance tests.

Assign an applicability rule defining the criteria to select the performance test based on which CPU option is selected.

If you want to use the TIAs in the applicability rule to determine when to include the option dependent operations, then while defining the TIAs, the TIAs must be assigned to application scope Configuration Matching. The TIAs are used in the configuration matching process to determine if a configuration already exists. The TIAs are also leveraged by Manufacturing to determine the operations that are to be executed to build a configured item.

Transactional item attributes are defined in Product Hub. Because TIA is associated with an item class, all items that belong to the item class will inherit the TIA. Based on the item class setup, you can define TIA for the top-level ATO model, optional components, or child ATO models. You can define an applicability rule using transactional item attributes with either numeric or string data type, as long as the associated value sets have a validation type of either independent or subset.

Create an Applicability Rule

To create an applicability rule, you must select the Option dependent check box in the Option Dependent Details region. This enables the Add icon. Click the Add icon to open the Add Applicability Rule dialog box. Unlike the Edit Work Definition Details page, the item structure visualization in the Add Applicability Rule dialog box shows the multilevel item structure of an ATO model. However, only the optional components are displayed. The current and future effective components and TIAs are shown based on the date selected in the Date list on the Edit Work Definition Details page. From the first-level components, you can expand the option classes to view the lower-level optional components. You can't expand a child ATO model. If you have defined the transactional item attributes, then they appear as the child nodes of a component. And expanding the transactional item attribute node shows the attribute values.

In the item structure, once you locate the item or TIA value that you need for defining the rule, you can do either of the following:

Drag and drop the item or TIA card to the Rule Text region.

Right-click the item or TIA card, from Actions menu, select: Insert into Rule Text.

After you drag and drop or insert the rule text, the Rule Text region shows the component hierarchy of the item or transactional item attribute. A component hierarchy is the relative path of the item node to the top-level ATO model node.

The following example shows the item structure and component hierarchy of ATO MODEL 1:

OPTION CLASS 1: ATO MODEL 1.OPTION CLASS 1

OPTION 11: ATO MODEL 1.OPTION CLASS 1.OPTION 11

OPTION 12: ATO MODEL 1.OPTION CLASS 1.OPTION 12

OPTION CLASS 2: ATO MODEL 1.OPTION CLASS 2

OPTION 21: ATO MODEL 1.OPTION CLASS 2.OPTION 21

OPTION 22: ATO MODEL 1.OPTION CLASS 2.OPTION 22

The Rule Text region has various operators that can be used to define an applicability rule. You can have a combination of items and TIAs in a rule, and build a complex expression using AND and OR conditions. Click the Validate button to validate the rule you're defining. If the rule fails to meet the valid syntax, an appropriate error message is shown. You have to correct the error before you can save the rule.

For numeric attributes, the valid operators are:

Not equal to

Less than or equal to

Greater Than

Greater than or equal to

For string attributes, the valid operators are:

DOESNOTCONTAIN

Valid rule syntax:

Keyword ITEM is used to specify an item, that's, ITEM is equal to 'ATO MODEL 1'.'OPTION CLASS 1'

Keyword TRANSACTIONALATTRIBUTE is used to specify a transactional item attribute, that's, 'ATO MODEL 1'.'OPTION CLASS 1'.'OPTION 11'. TRANSACTIONALATTRIBUTE ["Finish"] is equal to "Matte"

Item numbers are wrapped within single quotes

Transactional item attribute name and value are wrapped within double quotes

Dot is used as a separator in the component hierarchy

Operators are in upper case and aren't translatable

The Add Applicability Rule dialog box shows the display name of a transactional item attribute, which is translatable. If the value set used by a TIA is translatable, then the item structure visualization shows the internal name of the value and the translated value next to it in parenthesis. The applicability rule is evaluated against the value of the internal name and not the translated value.

Export Operation Item Assignments

The Export Operation Item Assignments action is available in the Actions menu in the Edit Work Definition page. It enables you to export the complete multilevel ATO model item structure to Excel in an indented view. The Excel captures the following information:

Displays the operations to which components are assigned.

Indicates if there is pending work in the Assignment Status column.

Lists other relevant item and item structure attributes such as User Item Type, Item Revision, and Structure Item Type.

Assignment status can be Complete, Incomplete, Explicit, or Implicit. An Explicit assignment status shows to which operation a component is directly assigned to. An Implicit assignment status applies to the children when their parent is directly assigned to an operation. Incomplete and Complete assignment status is derived by the application. In a parent-child scenario, if you have assigned all the children, then the assignment status for the parent is Complete, but if you haven't assigned all the children, then the assignment status for the parent is Incomplete.

You can quickly find out whether or not there is pending work by looking at the assignment status of the top level ATO model. If it's Incomplete, then it means you still have pending work in terms of operation item assignments. If it's Complete, then it means you have fully completed operation item assignments.

Related Topics

• Overview of Production Process Design
• Overview of Work Definitions
• Configured Item Work Definitions: Explained
• Define Common SCM Configuration: Define Advanced Item