Unity3D单例类模板类的实现

                                                           Unity3D单例类模板类的实现                                                                                                                                                                                                                                                

                                                                                                                                                                                                                                                                                                    By D.S.Qiu

尊重他人的劳动，支持原创，转载请注明出处：http.dsqiu.iteye.com

        

        无意中Unity工程中看到Singleton的类，因为之前D.S.Qiu在项目中也用了Singleton来做所有View的单例类模板，有种“英雄所见略同”的赶脚（虽然此处用法不当），所以贴出来分享下：

using UnityEngine;

/// <summary>
/// Be aware this will not prevent a non singleton constructor
///   such as `T myT = new T();`
/// To prevent that, add `protected T () {}` to your singleton class.
/// 
/// As a note, this is made as MonoBehaviour because we need Coroutines.
/// </summary>
public class Singleton<T> : MonoBehaviour where T : MonoBehaviour
{
	private static T _instance;
	
	private static object _lock = new object();
	
	public static T Instance
	{
		get
		{
			if (applicationIsQuitting) {
				Debug.LogWarning("[Singleton] Instance '"+ typeof(T) +
				                 "' already destroyed on application quit." +
				                 " Won't create again - returning null.");
				return null;
			}
			
			lock(_lock)
			{
				if (_instance == null)
				{
					_instance = (T) FindObjectOfType(typeof(T));
					
					if ( FindObjectsOfType(typeof(T)).Length > 1 )
					{
						Debug.LogError("[Singleton] Something went really wrong " +
						               " - there should never be more than 1 singleton!" +
						               " Reopenning the scene might fix it.");
						return _instance;
					}
					
					if (_instance == null)
					{
						GameObject singleton = new GameObject();


						_instance = singleton.AddComponent<T>();
						singleton.name = "(singleton) "+ typeof(T).ToString();
						
						DontDestroyOnLoad(singleton);
						
						Debug.Log("[Singleton] An instance of " + typeof(T) + 
						          " is needed in the scene, so '" + singleton +
						          "' was created with DontDestroyOnLoad.");
					} else {
						Debug.Log("[Singleton] Using instance already created: " +
						          _instance.gameObject.name);
					}
				}
				
				return _instance;
			}
		}
	}
	
	private static bool applicationIsQuitting = false;
	/// <summary>
	/// When Unity quits, it destroys objects in a random order.
	/// In principle, a Singleton is only destroyed when application quits.
	/// If any script calls Instance after it have been destroyed, 
	///   it will create a buggy ghost object that will stay on the Editor scene
	///   even after stopping playing the Application. Really bad!
	/// So, this was made to be sure we're not creating that buggy ghost object.
	/// </summary>
	public void OnDestroy () {
		applicationIsQuitting = true;
	}
}

 小结：

        别人实现的就是考虑到位，同步锁和程序退出的情况，D.S.Qiu实现的版本都没有做这样的考虑。不过，D.S,Qiu的View其实是用来管理UI的但没有继承MonoBehavior，只是一个普通的C#类，便于自己管理，不过这样有一个劣势就是不能使用MonoBehavior的行为，如协程等特性。

 

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