基於 MonoBehaviour ScriptableObject 的 Singleton 類
大多數 Singleton 示例使用 MonoBehaviour 作為基類。主要缺點是這個 Singleton 類僅在執行時存在。這有一些缺點：
- 除了更改程式碼之外，無法直接編輯單例欄位。
- 無法在 Singleton 上儲存對其他資產的引用。
- 無法將單例設定為 Unity UI 事件的目標。我最終使用我稱之為代理元件的東西，它唯一的建議是使用一行呼叫“
GameManager.Instance.SomeGlobalMethod()”的方法。
正如備註中所述，有些實現試圖使用 ScriptableObjects 作為基類來解決這個問題，但卻失去了 MonoBehavi 的執行時優勢。此實現通過在執行時使用 ScriptableObject 作為基類和關聯的 MonoBehavior 來解決此問題：
- 它是一種資產，因此可以像編輯任何其他 Unity 資產一樣在編輯器上更新其屬性。
- 它與 Unity 序列化過程很好地配合。
- 可以將單例的引用分配給編輯器中的其他資源（依賴項通過編輯器注入）。
- Unity 事件可以直接呼叫 Singleton 上的方法。
- 可以使用“SingletonClassName.Instance”從程式碼庫中的任何位置呼叫它
- 可以訪問執行時 MonoBehaviour 事件和方法，如：Update，Awake，Start，FixedUpdate，StartCoroutine 等。
/************************************************************
* Better Singleton by David Darias
* Use as you like - credit where due would be appreciated :D
* Licence: WTFPL V2, Dec 2014
* Tested on Unity v5.6.0 (should work on earlier versions)
* 03/02/2017 - v1.1
* **********************************************************/
using System;
using UnityEngine;
using SingletonScriptableObjectNamespace;
public class SingletonScriptableObject<T> : SingletonScriptableObjectNamespace.BehaviourScriptableObject where T : SingletonScriptableObjectNamespace.BehaviourScriptableObject
{
//Private reference to the scriptable object
private static T _instance;
private static bool _instantiated;
public static T Instance
{
get
{
if (_instantiated) return _instance;
var singletonName = typeof(T).Name;
//Look for the singleton on the resources folder
var assets = Resources.LoadAll<T>("");
if (assets.Length > 1) Debug.LogError("Found multiple " + singletonName + "s on the resources folder. It is a Singleton ScriptableObject, there should only be one.");
if (assets.Length == 0)
{
_instance = CreateInstance<T>();
Debug.LogError("Could not find a " + singletonName + " on the resources folder. It was created at runtime, therefore it will not be visible on the assets folder and it will not persist.");
}
else _instance = assets[0];
_instantiated = true;
//Create a new game object to use as proxy for all the MonoBehaviour methods
var baseObject = new GameObject(singletonName);
//Deactivate it before adding the proxy component. This avoids the execution of the Awake method when the the proxy component is added.
baseObject.SetActive(false);
//Add the proxy, set the instance as the parent and move to DontDestroyOnLoad scene
SingletonScriptableObjectNamespace.BehaviourProxy proxy = baseObject.AddComponent<SingletonScriptableObjectNamespace.BehaviourProxy>();
proxy.Parent = _instance;
Behaviour = proxy;
DontDestroyOnLoad(Behaviour.gameObject);
//Activate the proxy. This will trigger the MonoBehaviourAwake.
proxy.gameObject.SetActive(true);
return _instance;
}
}
//Use this reference to call MonoBehaviour specific methods (for example StartCoroutine)
protected static MonoBehaviour Behaviour;
public static void BuildSingletonInstance() { SingletonScriptableObjectNamespace.BehaviourScriptableObject i = Instance; }
private void OnDestroy(){ _instantiated = false; }
}
// Helper classes for the SingletonScriptableObject
namespace SingletonScriptableObjectNamespace
{
#if UNITY_EDITOR
//Empty custom editor to have cleaner UI on the editor.
using UnityEditor;
[CustomEditor(typeof(BehaviourProxy))]
public class BehaviourProxyEditor : Editor
{
public override void OnInspectorGUI(){}
}
#endif
public class BehaviourProxy : MonoBehaviour
{
public IBehaviour Parent;
public void Awake() { if (Parent != null) Parent.MonoBehaviourAwake(); }
public void Start() { if (Parent != null) Parent.Start(); }
public void Update() { if (Parent != null) Parent.Update(); }
public void FixedUpdate() { if (Parent != null) Parent.FixedUpdate(); }
}
public interface IBehaviour
{
void MonoBehaviourAwake();
void Start();
void Update();
void FixedUpdate();
}
public class BehaviourScriptableObject : ScriptableObject, IBehaviour
{
public void Awake() { ScriptableObjectAwake(); }
public virtual void ScriptableObjectAwake() { }
public virtual void MonoBehaviourAwake() { }
public virtual void Start() { }
public virtual void Update() { }
public virtual void FixedUpdate() { }
}
}
這裡有一個使用 SingletonScriptableObject（有很多註釋）的 GameManager 單例類示例：
using System;
using System.Collections;
using System.Collections.Generic;
using UnityEngine;
//this attribute is optional but recommended. It will allow the creation of the singleton via the asset menu.
//the singleton asset should be on the Resources folder.
[CreateAssetMenu(fileName = "GameManager", menuName = "Game Manager", order = 0)]
public class GameManager : SingletonScriptableObject<GameManager> {
//any properties as usual
public int Lives;
public int Points;
//optional (but recommended)
//this method will run before the first scene is loaded. Initializing the singleton here
//will allow it to be ready before any other GameObjects on every scene and will
//will prevent the "initialization on first usage".
[RuntimeInitializeOnLoadMethod(RuntimeInitializeLoadType.BeforeSceneLoad)]
public static void BeforeSceneLoad() { BuildSingletonInstance(); }
//optional,
//will run when the Singleton Scriptable Object is first created on the assets.
//Usually this happens on edit mode, not runtime. (the override keyword is mandatory for this to work)
public override void ScriptableObjectAwake(){
Debug.Log(GetType().Name + " created." );
}
//optional,
//will run when the associated MonoBehavioir awakes. (the override keyword is mandatory for this to work)
public override void MonoBehaviourAwake(){
Debug.Log(GetType().Name + " behaviour awake." );
//A coroutine example:
//Singleton Objects do not have coroutines.
//if you need to use coroutines use the atached MonoBehaviour
Behaviour.StartCoroutine(SimpleCoroutine());
}
//any methods as usual
private IEnumerator SimpleCoroutine(){
while(true){
Debug.Log(GetType().Name + " coroutine step." );
yield return new WaitForSeconds(3);
}
}
//optional,
//Classic runtime Update method (the override keyword is mandatory for this to work).
public override void Update(){
}
//optional,
//Classic runtime FixedUpdate method (the override keyword is mandatory for this to work).
public override void FixedUpdate(){
}
}
/*
* Notes:
* - Remember that you have to create the singleton asset on edit mode before using it. You have to put it on the Resources folder and of course it should be only one.
* - Like other Unity Singleton this one is accessible anywhere in your code using the "Instance" property i.e: GameManager.Instance
*/