Andrew Trice

Tuesday September 12, 2006

Singleton in AS3

I was explaining the singleton design pattern to a coworker today, and used Wikipedia as a source of information. There are examples of different languages on there, but no ActionScript! So, I decided to go ahead and add it. Here's the link to AS3 singleton example on wikipedia.

In case you didn't want to go to wikipedia...

package
{
    public class Singleton
    {
        private static var singleton : Singleton
		
        public static function getInstance() : Singleton
        {
            if ( singleton == null )
                singleton = new Singleton( arguments.callee );
            return singleton;
        }
	   
        //NOTE: AS3 does not allow for private or protected constructors
        public function Singleton( caller : Function = null ) 
        {	
            if( caller != Singleton.getInstance )
                throw new Error ("Singleton is a singleton class, use getInstance() instead");
			
            if ( Singleton.singleton != null )
                throw new Error( "Only one Singleton instance should be instantiated" );	
				
            //put instantiation code here
        }
    }
}