package

{

	import flash.errors.IllegalOperationError;

	import flash.events.EventDispatcher;

	import flash.utils.Dictionary;

	import flash.utils.getQualifiedClassName;

	public class DT1 extends EventDispatcher

	{

		private static var dict:Dictionary = new Dictionary();

		public function DT1()

		{

			trace("运行DT1 ");

			var ref:Class = this["constructor"] as Class;

			if (dict[ref])

			{

				throw new IllegalOperationError((getQualifiedClassName(this) + " 只允许实例化一次！"));

			}

			else

			{

				dict[ref] = this;

			}

		}

		/**

		         * 获取单例类，若不存在则创建

		         *

		         * @param ref继承自DT1的类

		         * @return

		         *

		         */

		public static function getInstanceOrCreate(ref:Class):*

		{

			if (dict[ref] == null)

			{

				dict[ref] = new ref();

			}

			return dict[ref];

		}

	}

}

package

{

	import flash.errors.IllegalOperationError;

	import flash.utils.getQualifiedClassName;

	public class DT2

	{

		private static var _instance:DT2 = null;

		public function DT2()

		{

			trace("运行DT2 ");

			if(_instance)

			 throw new IllegalOperationError(getQualifiedClassName(this)+" 只运行实例化一次！");

		}

		public static function getInstance():DT2

		{

			return _instance ||= new DT2();

		}

	}

}

package

{

	import flash.errors.IllegalOperationError;

	import flash.utils.getQualifiedClassName;

	public class DT3

	{

		private static var _instance:DT3 = null;

		public function DT3(instance:SureSingle=null)

		{

			if(instance==null)

			 throw new IllegalOperationError(getQualifiedClassName(this)+" 是单例！");

		}

		public static function getInstance():DT3

		{

			return _instance ||= new DT3(new SureSingle());

		}

	}

}

internal class SureSingle{}