AS3 Singletons, the other way
November 20th, 2007 | Posted by in ActionscriptSince you can’t declare a constructor private in AS3, there are a few methods out there to enforce a Singleton. A common way is to declare an internal SingletonEnforcer class outside the package: SingletonEnforcer, but the declaration of the Enforcer outside a package looks a bit “dirty” to me. Another way is to declare the singleton as a static variable, but this way you can’t decide when your singleton is instantiated.
So, why don’t just try nearly same with a local variable:
package { public class Singleton { private static var instance:Singleton; private static const checker:Object = {}; public function Singleton(initObj:Object) { if(initObj != checker) { throw new Error("Private constructor!"); } } public static function getInstance():Singleton { if(instance == null) { instance = new Singleton(checker); } return instance; } } }
Update: I found another nice solution by GSkinner: SingletonDemo.
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