Singleton Pattern

One of the design patterns in the Object-Oriented-Programming languages like ActionScript 3.0.
The Singleton design pattern is used to limit a class to one instance and provide global access to that instance
Common examples include classes that manage resources that are intrinsically singular such as

1. Selection focus
2. Navigation history
3. Window depth
4. Class that manages the state of user’s cursor
5. Class that loads application setting from an XML file and provide access to those settings

Essential features of Singleton class

• A private static property that holds the single instance of the class
• A public static method that provides access to the single instance if it’s created and creates the single instance if it hasn’t been created yet
• A way of restricting access to instantiating the class

Example – Creating a Singleton

package
{
public class MyClass
{
private static var _instance:MyClass

public function MyClass(enforcer:SingletonEnforcer)
{

}
public static function getInstance():MyClass
{
if(MyClass._instance == null)
{
MyClass._instance = new MyClass(new SingletonEnforcer());
}
}
}
}

class SingletonEnforcer {}

Invoking a Singleton inside another class
MyClass.getInstance()