Why is this an issue?

A typical code smell known as unused function parameters refers to parameters declared in a function but not used anywhere within the function’s body. While this might seem harmless at first glance, it can lead to confusion and potential errors in your code. Disregarding the values passed to such parameters, the function’s behavior will be the same, but the programmer’s intention won’t be clearly expressed anymore. Therefore, removing function parameters that are not being utilized is considered best practice.

Exceptions

The rule ignores the following cases:

• event handlers.
• overriding methods.
• all methods in classes implementing one or more interfaces.
• empty methods or methods where the body consists of a single comment or a single throw statement (i.e. where the intention is to simulate an abstract class).

override function doSomething(a:int):void {    // ignored
  compute(a);
}

...

class AbstractSomething {
  public function doSomething(a:int) {  // ignored
    throw new IllegalOperationError("doSomething() is abstract");
  }

...

interface I {
  function action(a:int, b:int);
}

class C extends I {
  function action(a:int, b:int) { // ignored
    return doSomethignWith(a);
  }
}

function clickHandler(event:MouseEvent):void { // ignored
   trace("click");
}

How to fix it

Having unused function parameters in your code can lead to confusion and misunderstanding of a developer’s intention. They reduce code readability and introduce the potential for errors. To avoid these problems, developers should remove unused parameters from function declarations.

Code examples

Noncompliant code example

function doSomething(a:int, b:int):void      // "b" is unused
{
  compute(a);
}

Compliant solution

function doSomething(a:int):void
{
  compute(a);
}