You can specify the object that a function is applied to and the parameter values that are passed to the function, using the call
and apply
methods of the Function object. Every function in ActionScript is represented by a Function object, so all functions support the call
and apply
methods. When you create a custom class using a constructor function, or when you define methods for a custom class using a function, you can invoke the call
and apply
methods for the function.
The Function.call
method invokes the function represented by a Function object.
In almost all cases, the function call operator (()
) may be used instead of the call
method. The function call operator creates code that is concise and readable. The call
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 in the following:
myObject.myMethod(1, 2, 3);
In some situations, you may 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)
For more information, see Function.call()
.
To invoke a function using the Function.call method:
myFunction
.call(thisObject
,parameter1
, ...,parameterN
)
The method takes the following parameters:
thisObject
specifies the value of this
within the function body. parameter1
..., parameterN
specify parameters to be passed to the myFunction
. You can specify zero or more parameters.The Function.apply
method specifies the value of this
to be used within any function that ActionScript calls. This method also specifies the parameters to be passed to any called function.
The parameters are specified as an Array object. This is often useful when the number of parameters to be passed is not known until the script actually executes.
For more information, see Function.apply()
.
To specify the object to which a function is applied using the Function.apply method:
myFunction
.apply(thisObject
,argumentsObject
)
The method takes the following parameters:
thisObject
specifies the object that myFunction
is applied to.argumentsObject
defines an array whose elements are passed to myFunction
as parameters.