So I was coding this game class where I have multiple kind of monsters but I want to use the same functions without checking what kind of monster it is. This is a case where polymorphism comes in handy. The thing is I didn’t do my classes of monster using inheritance (which maybe I should have done), so in order to use polymorphism, I have to create an interface with the public methods common to all my monster classes. So I open the Colin Moock book and start looking at how to code interfaces. Here is a list of quick facts that will help you while doing so.

• You have to list all public methods that will be common for the classes that implements this interface;
• You do so by writing the definition of the function, its name, its parameters and its return type;
• You don’t have to open and close curly braces after the method definition
• You don’t specify if the method is private, public or protected (that’s kind of obvious but I did that mistake)
• interface can only extend other interfaces
• a class can implement more than one interface

So here is an example of an interface in As3:

package com.mutantfarm.monster{
  public interface IMonster {
    function getShot(damage:uint):void;
    function getCanShoot():Boolean;
  }
}

Here is how my visual class implements this interface while also extending the MovieClip class:

public class spriteMouton extends MovieClip implements IMonster{

It is important that you put the extend keyword before the implement keyword.

So most of what I just wrote about was details about interfaces, but when you start coding, all these details are important to know.

Here are two more article I wrote about interfaces:

• Another good use of interfaces
• External Preloader; more complex cases