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91 行
3.0 KiB
91 行
3.0 KiB
using UnityEngine;
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/// <summary>
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/// Be aware this will not prevent a non singleton constructor
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/// such as `T myT = new T();`
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/// To prevent that, add `protected T () {}` to your singleton class.
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/// </summary>
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public class Singleton<T> : MonoBehaviour where T : MonoBehaviour
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{
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private static T _instance;
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private static object _lock = new object();
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public static T Instance
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{
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get
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{
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if (applicationIsQuitting)
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{
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Debug.LogWarning("[Singleton] Instance '" + typeof(T) +
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"' already destroyed on application quit." +
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" Won't create again - returning null.");
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return null;
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}
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lock (_lock)
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{
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if (_instance == null)
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{
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_instance = (T)FindObjectOfType(typeof(T));
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if (FindObjectsOfType(typeof(T)).Length > 1)
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{
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Debug.LogError("[Singleton] Something went really wrong " +
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" - there should never be more than 1 singleton!" +
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" Reopening the scene might fix it.");
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return _instance;
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}
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if (_instance == null)
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{
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GameObject singleton = new GameObject();
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_instance = singleton.AddComponent<T>();
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singleton.name = "(singleton) " + typeof(T).ToString();
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Debug.Log("[Singleton] An instance of " + typeof(T) +
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" is needed in the scene, so '" + singleton +
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"' was created.");
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}
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else
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{
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//Debug.Log("[Singleton] Using instance already created: " + _instance.gameObject.name);
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}
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}
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return _instance;
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}
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}
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}
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private static bool IsDontDestroyOnLoad()
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{
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if (_instance == null)
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{
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return false;
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}
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// Object exists independent of Scene lifecycle, assume that means it has DontDestroyOnLoad set
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if ((_instance.gameObject.hideFlags & HideFlags.DontSave) == HideFlags.DontSave)
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{
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return true;
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}
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return false;
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}
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private static bool applicationIsQuitting = false;
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/// <summary>
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/// When Unity quits, it destroys objects in a random order.
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/// In principle, a Singleton is only destroyed when application quits.
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/// If any script calls Instance after it have been destroyed,
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/// it will create a buggy ghost object that will stay on the Editor scene
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/// even after stopping playing the Application. Really bad!
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/// So, this was made to be sure we're not creating that buggy ghost object.
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/// </summary>
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public void OnDestroy()
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{
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if (IsDontDestroyOnLoad())
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{
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applicationIsQuitting = true;
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}
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}
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}
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