go to previous page

- discuss this tutorial -

go to next page

11. Interface

When it comes to OOP, besides inheritance, another useful concept is the interface. Like Java and C#, ActionScript does not support multiple inheritance (i.e. a subclass with more than one superclass). This is because multiple inheritance can be a nightmare to debug if used improperly, getting into circular referencing and other sticky situations. In a carefully designed application, using interfaces can achieve similar results with less headaches.

An interface is a contract that specifies what methods must be implemented by a class implementing it; usually there is no relationship between the interface and the implementing class. In an interface, there is no code or property, only method signatures. Interfaces are written almost like classes, except:

• They do not have properties
• They ony include method names, arguments, their types, and return types
• Method definitions end with a semi-colon, not curly braces

Here is an example of a Draggable class (the name of an interface is usually prefixed with the letter 'I'):

interface IDraggable {
   public function startDrag():Void;
   public function stopDrag():Void;
   public function isDragging():Boolean;
}

class Child extends Parent implements IDraggable {
   public function Child() {
      // add Child constructor code
   }
   public function startDrag():Void {
      // implement the code for startDrag();
   }
   public function stopDrag():Void {
      // implement the code for stopDrag();
   }
   public function isDragging():Boolean {
      // implement the code for isDragging();
   }
}

go to previous page

- discuss this tutorial -

go to next page