Actionscript Cookbook

12.4. Adding Custom Methods to an Object Instance

Problem

You want to add custom methods to an object.

Solution

Assign a function definition (or a reference to one) to a custom property of an object that is already instantiated.

Discussion

You can add functionality to objects (instances of a class) by assigning new methods to them. First, define a function. Then store a reference to the function in a custom property of the object. That is, the definitions of an object’s methods are stored as properties of the same object.

This example stores a function in the custom property methodProp:

myObject = new Object(  );
myObject.methodProp = function (  ) {
  trace("Hello World");
};

The preceding example assigns a method to an object using an anonymous function. However, you can also use object properties to store references to named functions. The following example stores a reference to the named function, myMethodFunction( ), in the property myMethod:

// Define a named function.
function myMethodFunction (  ) {
  trace(this.myProperty);
}

// Create a new object. You can assign custom methods to any kind of object (movie
// clip, array, etc.), but this example uses a generic object of the Object class. myObject = new Object( ); // Create a custom property on the object. This is not necessary, per se, but we use // it here to illustrate that when a function is called as a method of an object, the // function has access to all the properties of that object by means of // self-references (using the ...