U3D点滴－单例模式

来源：互联网发布：做淘宝月收入多少编辑：程序博客网时间：2024/05/25 20:00

例如：对于一个音乐管理类

usingUnityEngine;

publicclass MusicManager : MonoBehaviour 

{

    publicvoid Play()

{

        //Play some audio!

}

}

现在要调用来播放音乐，如下代码

Object.FindObjectOfType < MusicManager > ().Play();

以上的代码不仅难懂而且不安全，比较的好方式如下代码：

var musicManager = Object.FindObjectOfType < MusicManager >();

if ( musicManager != null )

{

musicManager.Play ();

}

以上的代码运行没有问题，但是每次调用的话会比较麻烦。

现在就用单例模式来创建代码：

publicclass MusicManager : MonoBehaviour 

{

    //We make a static variable to our MusicManager instance

    publicstatic MusicManager instance { get;privateset; }

    //When the object awakens, we assign the static variable

    voidAwake() 

{

        instance = this;

}

    publicvoid Play()

{

        //Play some audio!

}

}

//...

//Now in another class, we can call Play() by using the static variable!

publicclass LevelController : MonoBehaviour

{

    voidPlayMusic()

{

        MusicManager.instance.Play();

}

}

这样的方式叫做lazy Singleton(偷懒的单例模式吗？！)

这样使用要注意一个地方就是调用的时间，就是如果要使用不能在awake（）方法里面，以保证这个实例不为null

比如，Start()方法就可以。

以下是标准的单例模式

publicclass MusicManager : MonoBehaviour 
{
    //Here is a private reference only this class can access
    privatestatic MusicManager _instance;
 
    //This is the public reference that other classes will use
    publicstatic MusicManager instance
    {
        get
        {
            //If _instance hasn't been set yet, we grab it from the scene!
            //This will only happen the first time this reference is used.
            if(_instance == null)
                _instance = GameObject.FindObjectOfType<MusicManager>();
            return_instance;
        }
    }
 
    publicvoid Play()
    {
        //Play some audio!
    }
}

持续的单例

有时候你可能要在不同的场景里面使用单例

publicclass MusicManager : MonoBehaviour 
{
    privatestatic MusicManager _instance;
 
    publicstatic MusicManager instance
    {
        get
        {
            if(_instance == null)
            {
                _instance = GameObject.FindObjectOfType<MusicManager>();
 
                //Tell unity not to destroy this object when loading a new scene!
                DontDestroyOnLoad(_instance.gameObject);
            }
 
            return_instance;
        }
    }
 
    voidAwake() 
    {
        if(_instance == null)
        {
            //If I am the first instance, make me the Singleton
            _instance = this;
            DontDestroyOnLoad(this);
        }
        else
        {
            //If a Singleton already exists and you find
            //another reference in scene, destroy it!
            if(this!= _instance)
                Destroy(this.gameObject);
        }
    }
 
    publicvoid Play()
    {
        //Play some audio!
    }
}

DontDestroyOnLoad() will maintain all scripts that are placed on the same GameObject as your singleton.

For this reason it’s usually a good idea to put a singleton on it’s own GameObject alone.

Other Notes:

DontDestroyOnLoad() only needs to be used on objects inheriting MonoBehaviour. A static reference in a normal class will maintain its data across scenes.
In Unity, if you have a reference to a GameObject or MonoBehaviour that has been destroyed, it will equal null. The singleton examples above use this to their advantage.

以上是e文，自己体会吧

原文引用：http://unitypatterns.com/singletons/

0 0