MACROMEDIA FLASH MX 2004 - ACTIONSCRIPT, Reference Manual

Page: 805 / 816

About ActionScript 1 805
Invoking a function using the Function.call() method in ActionScript 1
The
Function.call()
method invokes the function represented by a Function object.
In almost all cases, the function call operator (
()
) can 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()
in Chapter 12, “ActionScript Dictionary,”
on page 205 .
To invoke a function using the Function.call method:
•
Use the following syntax.
myFunction .call( thisObject , parameter1 , ..., parameterN )
The method takes the following parameters:
■
The parameter
thisObject
specifies the value of
this
within the function body.
■
The parameters
parameter1 ..., parameterN
specify parameters to be passed to
myFunction
. You can specify zero or more parameters.
Specifying the object to which a function is applied using Function.apply()
in ActionScript 1
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()
in Chapter 12, “ActionScript Dictionary,”
on page 205 .
To specify the object to which a function is applied using Function.apply():
•
Use the following syntax.
myFunction .apply( thisObject , argumentsObject )
The method takes the following parameters:
■
The parameter
thisObject
specifies the object that
myFunction
is applied to.
■
The parameter
argumentsObject
defines an array whose elements are passed to
myFunction
as parameters.