User Guide

Function.call() 293
Function.call()
Availability
Flash Player 6.
Usage
myFunction.call(thisObject:Object, parameter1, ..., parameterN)
Parameters
thisObject
An object that specifies the value of this within the function body.
parameter1 A parameter to be passed to the myFunction. You can specify zero or
more parameters.
parameterN
Returns
Nothing.
Description
Method; invokes the function represented by a Function object. Every function in ActionScript is
represented by a Function object, so all functions support this method.
In almost all cases, the function call (
()) operator can be used instead of this method. The
function call operator produces code that is concise and readable. This method is primarily useful
when the
this parameter of the function invocation needs to be explicitly controlled. Normally,
if a function is invoked as a method of an object, within the body of the function,
this is set to
myObject, as shown in the following example:
myObject.myMethod(1, 2, 3);
In some situations, you might want this to point somewhere else; for example, if a function must
be invoked as a method of an object, but is not actually stored as a method of that object:
myObject.myMethod.call(myOtherObject, 1, 2, 3);
You can pass the value null for the thisObject parameter to invoke a function as a regular
function and not as a method of an object. For example, the following function invocations
are equivalent:
Math.sin(Math.PI / 4)
Math.sin.call(null, Math.PI / 4)
Example
The following example uses Function.call() to make a function behave as a method of another
object, without storing the function in the object:
function myObject() {
}
function myMethod(obj) {
trace("this == obj? " + (this == obj));
}