[유니티 스크립트 소스] 싱글톤(Singleton) 2

 

using UnityEngine;
using System;
using UnityEngine.SceneManagement;

/// <summary>
/// Singleton attribute work with singleton class.
/// </summary>
public class SingletonAttribute : Attribute
{
    //Tell if this singleton has to create himself if he is called and not present in the scene.
    public bool createIfNotPresent;

    public SingletonAttribute(bool b)
    {
        createIfNotPresent = b;
    }
}


/// <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>
//[ExecuteInEditMode]
[SingletonAttribute(true)]
public class Singleton<T> : MonoBehaviour where T : Singleton<T>
{

    private static T _instance = null;
    private static bool applicationIsQuitting = false;

    public static T Instance
    {
        get
        {
            if (_instance == null)
            {
                _instance = (T)FindObjectOfType(typeof(T));

                if (_instance == null)
                {
                    if (!applicationIsQuitting)
                    {
                        var customAttributes = (SingletonAttribute[])typeof(T).GetCustomAttributes(typeof(SingletonAttribute), true);

                        if (customAttributes.Length > 0)
                        {
#if EQUILIBRE_GAMES_DEBUG
                            Debug.Log("[Singleton] An instance of " + typeof(T) +
                                      " is needed in the scene");
#endif

                            var myAttribute = customAttributes[0];
                            bool createNewSingleton = myAttribute.createIfNotPresent;

                            if (createNewSingleton)
                            {
                                GameObject singleton = new GameObject();
                                singleton.name = typeof(T).Name;
                                _instance = singleton.AddComponent<T>();
#if EQUILIBRE_GAMES_DEBUG
                                Debug.Log("[Singleton] An instance of " + typeof(T) +
                                         " was created");
#endif
                                _instance.OnAwake();
                            }
                        }
                        else
                        {
#if EQUILIBRE_GAMES_DEBUG

                            Debug.Log("[Singleton] An instance of " + typeof(T) +
                                      " is needed in the scene");
#endif

                            GameObject singleton = new GameObject();
                            singleton.name = typeof(T).Name;
                            _instance = singleton.AddComponent<T>();
#if EQUILIBRE_GAMES_DEBUG
                            Debug.Log("[Singleton] An instance of " + typeof(T) +
                                     " was created");
#endif
                            _instance.OnAwake();
                        }
                    }
                }
                else
                    _instance.OnAwake();
            }
            return _instance;
        }
    }

    public virtual void OnAwake() { }

    void Awake()
    {
        if (!_instance)
        {
            _instance = this as T;
            _instance.OnAwake();
        }

        CheckMultipleInstance();
    }

    static void CheckMultipleInstance()
    {
        if (FindObjectsOfType(typeof(T)).Length > 1)
        {
#if EQUILIBRE_GAMES_DEBUG  || UNITY_EDITOR
            Debug.LogError("[Singleton<" + typeof(T) + ">] Something went really wrong " +
                           " - there should never be more than 1 singleton!" +
                           " Reopenning the scene might fix it.");
#endif
        }
    }

    public virtual void OnApplicationQuit()
    {
        applicationIsQuitting = true;
    }
}