How to implement singleton pattern in actionscript 3

Posted on October 23, 2009, 10:02 pm, by Van Nhu.

In actionscript 3 one can not use private scope for constructor and you need a workaround to implement simgleton pattern. Following is one way that I use

package
{
	public class Singleton
	{
		private static var instance:Singleton;
		private static var isAllowedInstance:Boolean;
 
		public function Singleton() {
			if (!isAllowedInstance) {
				throw new Error("Please use " + 
						"Singleton.getInstance()" + 
						"instead of new keyword");
			}
			this.init();
		}
 
		private function init():void {
			trace("init stuffs");
		}
 
		public static function getInstance():Singleton {
			if (null == instance) {
				isAllowedInstance = true;
				instance = new Singleton();
				isAllowedInstance = false;
			}
			return instance;
		}
 
		public function singsing():void {
			trace("singsing");
		}
	}
}

This will cause an error if someone uses the new keyword

var singleton:Singleton = new Singleton();

It will work fine if you use it like this

var singleton:Singleton = Singleton.getInstance();

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Posted under: Actionscript

One Comment

  1. How to Implement an Effective Weight Loss Program | Real Weight Loss Reports says:
    October 25, 2009 at 11:05 pm

    [...] Howtos » Blog Archive » How to implement singleton pattern in … [...]

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