remove this useless assignment to local variable in c#

SonarQube displaying to 'remove this useless assignment to local variable'

Why is SonarQube giving this error? How should I fix it? Their rule page does not specify the solution,

Remove this useless assignment to local variable validateAddressRequest.

 Answers

This site says that the error occurs when:

A value is assigned to a variable or property, but either that location is never read later on, or its value is always overwritten before being read. This means that the original assignment has no effect, and could indicate a logic error or incomplete code.

On the first line of the if block, you assign to validateAddressRequest , but then on the third line of the if block, you overwrite validateAddressRequest without having read the previously assigned variable. So the first line is useless.

Declare validateAddressRequest only when calling convertToValidateRequest instead.

Note that you almost certainly don't need the type annotation - if Typescript knows that convertToValidateRequest returns a ValidateAddressRequest already, there's no need to do so again with the new variable. You can do so if you think it's unclear otherwise, or if you don't have type Intellisense, but it may just be noise.

If you were declaring the variable with let so as to enable assignment to it in the future, keep in mind that it's best to avoid reassignment whenever possible, and it's almost always possible to avoid reassignment. If you need another variable that contains a ValidateAddressRequest , give it a different variable name so that you can use const to declare both variables; that makes the code more understandable at a glance, when a reader can be sure that a particular variable reference isn't ever going to be reassigned.

freddiejarretk

"Remove this useless assignment to local variable", but the assignment is not useless

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Michael Gumowski

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Solving Sonar's 'Remove Useless Assignment of Local Variable' Error in Swift

Abstract: Learn how to resolve SonarQube's 'Remove Useless Assignment of Local Variable' error in Swift by understanding its cause and using different workarounds.

Solving Sonar's "Remove Useless Assignment to Local Variable" Error in Swift

Sonar is a popular tool used for code analysis and review. It helps developers identify and fix issues in their code, making it more readable, maintainable, and secure. One common issue that Sonar flags is the "Remove Useless Assignment to Local Variable" error in Swift. This error occurs when a local variable is assigned a value that is not used in the code. In this article, we will discuss how to solve this error in Swift.

Understanding the Error

To understand the error, let's consider an example:

In this example, we declare two local variables, x and y. We assign the value 5 to x and then calculate the value of y by multiplying x by 2. However, we never use the value of x again in the code. Therefore, Sonar flags the assignment of x as a useless assignment.

Solving the Error

To solve the error, we need to ensure that every local variable is used in the code. We can do this by either using the variable or removing its declaration. In the above example, we can remove the declaration of x, as it is not used in the code:

Alternatively, we can use the value of x in the code:

In this example, we print the value of x to the console, ensuring that it is used in the code.

Using Sonar to Identify Useless Assignments

Sonar can help us identify useless assignments in our code. To do this, we need to configure Sonar to analyze our Swift code. We can do this by installing the SonarSwift plugin and configuring it to analyze our project. Once we have done this, Sonar will flag any useless assignments in our code, allowing us to fix them.

The "Remove Useless Assignment to Local Variable" error in Swift is a common issue that Sonar flags. To solve this error, we need to ensure that every local variable is used in the code. We can do this by either using the variable or removing its declaration. Sonar can help us identify useless assignments in our code, allowing us to fix them and improve the quality of our code.

Remove Useless Assignment to Local Variable

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Tags: :  Swift SonarQube Software Development

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Rubocopエラー「Useless assignment to variable」の解決例

上記エラーを調べると、「使っていないローカル変数の定義がある」というエラーのようで 削除すれば解決するとの事でした。

しかし、今回はちゃんと使っている内容で、書き方の問題のようでした。 以下のように、if文などの後に 明示的に使用している記載が必要 とのことでした。

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Useless assignment to local variable ¶

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A value is assigned to a variable, but either it is never read, or its value is always overwritten before being read. This means that the original assignment has no effect, and could indicate a logic error or incomplete code.

Recommendation ¶

Remove assignments to variables that are immediately overwritten, or use the blank identifier _ as a placeholder for return values that are never used.

In the following example, a value is assigned to a , but then immediately overwritten, a value is assigned to b and never used, and finally, the results of a call to fmt.Println are assigned to two temporary variables, which are then immediately overwritten by a call to function .

The result of calculateValue is never used, and if calculateValue is a side-effect free function, those assignments can be removed. To ignore all the return values of fmt.Println , you can simply not assign it to any variables. To ignore only certain return values, use _ .

References ¶

Wikipedia: Dead store .

The Go Programming Language Specification: Blank identifier .

Common Weakness Enumeration: CWE-563 .

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Implicitly typed local variables (C# Programming Guide)

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Local variables can be declared without giving an explicit type. The var keyword instructs the compiler to infer the type of the variable from the expression on the right side of the initialization statement. The inferred type may be a built-in type, an anonymous type, a user-defined type, or a type defined in the .NET class library. For more information about how to initialize arrays with var , see Implicitly Typed Arrays .

The following examples show various ways in which local variables can be declared with var :

It is important to understand that the var keyword does not mean "variant" and does not indicate that the variable is loosely typed, or late-bound. It just means that the compiler determines and assigns the most appropriate type.

The var keyword may be used in the following contexts:

On local variables (variables declared at method scope) as shown in the previous example.

In a for initialization statement.

In a foreach initialization statement.

In a using statement.

For more information, see How to use implicitly typed local variables and arrays in a query expression .

var and anonymous types

In many cases the use of var is optional and is just a syntactic convenience. However, when a variable is initialized with an anonymous type you must declare the variable as var if you need to access the properties of the object at a later point. This is a common scenario in LINQ query expressions. For more information, see Anonymous Types .

From the perspective of your source code, an anonymous type has no name. Therefore, if a query variable has been initialized with var , then the only way to access the properties in the returned sequence of objects is to use var as the type of the iteration variable in the foreach statement.

The following restrictions apply to implicitly-typed variable declarations:

var can only be used when a local variable is declared and initialized in the same statement; the variable cannot be initialized to null, or to a method group or an anonymous function.

var cannot be used on fields at class scope.

Variables declared by using var cannot be used in the initialization expression. In other words, this expression is legal: int i = (i = 20); but this expression produces a compile-time error: var i = (i = 20);

Multiple implicitly-typed variables cannot be initialized in the same statement.

If a type named var is in scope, then the var keyword will resolve to that type name and will not be treated as part of an implicitly typed local variable declaration.

Implicit typing with the var keyword can only be applied to variables at local method scope. Implicit typing is not available for class fields as the C# compiler would encounter a logical paradox as it processed the code: the compiler needs to know the type of the field, but it cannot determine the type until the assignment expression is analyzed, and the expression cannot be evaluated without knowing the type. Consider the following code:

bookTitles is a class field given the type var . As the field has no expression to evaluate, it is impossible for the compiler to infer what type bookTitles is supposed to be. In addition, adding an expression to the field (like you would for a local variable) is also insufficient:

When the compiler encounters fields during code compilation, it records each field's type before processing any expressions associated with it. The compiler encounters the same paradox trying to parse bookTitles : it needs to know the type of the field, but the compiler would normally determine var 's type by analyzing the expression, which isn't possible without knowing the type beforehand.

You may find that var can also be useful with query expressions in which the exact constructed type of the query variable is difficult to determine. This can occur with grouping and ordering operations.

The var keyword can also be useful when the specific type of the variable is tedious to type on the keyboard, or is obvious, or does not add to the readability of the code. One example where var is helpful in this manner is with nested generic types such as those used with group operations. In the following query, the type of the query variable is IEnumerable<IGrouping<string, Student>> . As long as you and others who must maintain your code understand this, there is no problem with using implicit typing for convenience and brevity.

The use of var helps simplify your code, but its use should be restricted to cases where it is required, or when it makes your code easier to read. For more information about when to use var properly, see the Implicitly typed local variables section on the C# Coding Guidelines article.

• C# Reference
• Implicitly Typed Arrays
• How to use implicitly typed local variables and arrays in a query expression
• Anonymous Types
• Object and Collection Initializers
• LINQ (Language-Integrated Query)
• Iteration statements
• using statement

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