flash document_class_value

Since the introduction of ActionScript 2, developers were used to creating a class which served as a point of entry to their application. This instantiated other objects which needed to access the main timeline. They therefore had to give a reference to the main timeline.

It was therefore quite common to find the following code on an image in the timeline:

var myApplication:Application = new Application ( this );

The application could also be initialised using a simple static method:

Application.initialise ( this );

Other developers used another technique consisting of changing the execution context from the main class with the following code:

this.__proto__= Application.prototype;
Application['apply']( this , null );

By using the keyword this in the class instance Application we reference the main timeline. ActionScript 3 integrates a new functionality called Document Class allowing us to avoid having to resort to these old practices.