An example of the Singleton pattern in ActionScript

SingletonExample.as

/*
  This code comes from http://www.darronschall.com/weblog/2007/11/actionscript-3-singleton-redux.cfm
*/

// in SingletonExample.as
package com.thefifthcircuit.util {
  public class SingletonExample {
    public var foo:String;
        
    private static const inst:SingletonExample = new SingletonExample(SingletonLock);
        
    public static function get instance():SingletonExample { return inst; }
    public function SingletonExample(lock:Class) {
      if(lock != SingletonLock) throw new Error("Invalid Singleton access. Use LoaderSingleton.instance.");
        
      foo = "bar";
    }
  }
}

// in SingletonLock.as
package com.thefifthcircuit.util {
  public class SingletonLock {}
}