Object-Oriented Design Pattern Summary 02 [Singleton Pattern]

Singleton Pattern【Singleton Pattern】【Singleton Pattern】

Guarantees that there is only one instance of a class, and provides a global access point to that instance.

Example 1:

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public class  Singleton { public static readonly  Singleton Instance; /// <summary> /// Static constructor, which ensures multi-thread safety. In a multithreaded state, only one thread can access the static constructor. /// Static constructor, can only implement a static constructor with no parameters. /// You can use attributes to pass instantiated parameters. Or use the method to achieve. /// </summary> static  Singleton()     {         Instance =  new  Singleton();     } private  Singleton() { } }

 

Example 2: [Simplified writing of Example 1]

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class  Singleton {      public static readonly  Singleton Instance =  new  Singleton(); //Can automatically generate static constructors. private  Singleton() { } }

 

Example 3: [with parameters]

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/// <summary> /// Multi-threaded singleton mode with parameters /// </summary> public class  Singleton { private static  volatile  Singleton instance =  null ; // Prevent compiler fine-tuning. private static object  lockHelper =  new object (); //helper private  Singleton( int  i) { } public static  Singleton GetInstance( int  i)     { if  (instance ==  null )         { lock  (lockHelper) //lock             {                                                                        if  (instance ==  null ) //双检查                 {                     instance =  new  Singleton(i);                 }             }         }          return  instance;     } }