项目中的单例如何管理

在项目中，我们往往会使用到单例，当想清理一下单例了，该怎么做呢？本篇文章提供一个单例管理思路。

将项目中的单例分为两大类，一类是可以被清理的，一类是不可以被清理。定义两个单例的基类，项目中用到的单例，根据需求从这两个基类中选择性的派生。再另外定义一个类，类中定义两个字典，分别存放两种单例的所有实例，当需要实例的时候，分别从对应的字典中去取。对于可被清理的单例，通过 event 链去清理，这样看着要比遍历容器去清理要清爽的多。下面直接上代码。

不可被清理的单例基类:

public class ManagerSingleton<T> where T : class, new()
{
    private static T _instance;

    public static T Instance
    {
        get
        {
            if (null == _instance)
            {
                _instance = ApplicationManager.GetSingleton(typeof(T).FullName) as T;
            }
            return _instance;
        }
    }
}

可被清理的单例基类:

public class ReleaseSingleton<T> where T : class, new()
{
    private static T _instance;

    public static T Instance
    {
        get
        {
            if (null == _instance)
            {
                _instance = ApplicationManager.GetReleaseSingleton(typeof(T).FullName) as T;
                ApplicationManager.eventReleaseSingleton -= Release;
                ApplicationManager.eventReleaseSingleton += Release;
            }
            return _instance;
        }
    }

    static void Release()
    {
        _instance = null;
    }
}

单例管理类:

using System;
using System.Collections.Generic;
using UnityEngine;

public class ApplicationManager
{
    static private Dictionary<string, object> dictSingleton = new Dictionary<string, object>();         //存放所有 不可被 清理的单例
    static private Dictionary<string, object> dictSingletonRelease = new Dictionary<string, object>();  //存放所有 可以被 清理的单例

    #region 不可被清理单例
    public static object GetSingleton(string singletonType)
    {
        object singleton;

        if (!dictSingleton.TryGetValue(singletonType, out singleton))
        {
            singleton = Activator.CreateInstance(Type.GetType(singletonType));
            dictSingleton.Add(singletonType, singleton);
        }

        return singleton;
    }

    public static void RemoveSingleton(string singletonType)
    {
        if (dictSingleton.ContainsKey(singletonType))
        {
            dictSingleton.Remove(singletonType);
        }
    }
    #endregion

    #region 可以被清理单例
    public static object GetReleaseSingleton(string singletonType)
    {
        Debug.Log(singletonType);
        object singleton;
        if (!dictSingletonRelease.TryGetValue(singletonType, out singleton))
        {
            singleton = Activator.CreateInstance(Type.GetType(singletonType));
            dictSingletonRelease.Add(singletonType, singleton);
        }

        return singleton;
    }

    public static void RemoveReleaseSingleton(string singletonType)
    {
        if (dictSingletonRelease.ContainsKey(singletonType))
        {
            dictSingletonRelease.Remove(singletonType);
        }
    }
    #endregion

    #region 单例清理

    public delegate void DeleReleaseSingleton();
    public static event DeleReleaseSingleton eventReleaseSingleton;

    public static void ReleaseAllSingleton()
    {
        if (null != eventReleaseSingleton)
        {
            eventReleaseSingleton();
            eventReleaseSingleton = null;
        }
        dictSingletonRelease.Clear();

        GC.Collect();
        GC.WaitForPendingFinalizers(); //挂起当前线程，直到处理终结器队列的线程清空该队列为止。
    }

    #endregion
}

当需要清理的时候，调用管理类中的方法即可。