objective-c中的Singleton单例模式的完整实现示例

Objective中单例模式的实现，应该是比较完整的包括了objc的单例的各个点。详细看代码注释，注意最后用c++的析构函数实现instance的释放，所以源文件类型必须是.mm格式。

Singleton.h

// //  Singleton.h //  singleton // //  Created by leondun on 11-4-20. //  Copyright 2011 leondun. All rights reserved. // #import <Foundation/Foundation.h> @interface Singleton : NSObject { } +(Singleton *)getInstance; @end

Singleton.mm

#import "Singleton.h" static Singleton * instance = nil; @interface Singleton(privateMethods) -(void)realRelease; @end @implementation Singleton //获取单例 +(Singleton *)getInstance {     @synchronized(self) {         if (instance == nil) {             [[self alloc] init];             }     }     return instance; } //唯一一次alloc单例，之后均返回nil + (id)allocWithZone:(NSZone *)zone {     @synchronized(self) {         if (instance == nil) {             instance = [super allocWithZone:zone];             return instance;         }     }     return nil; } //copy返回单例本身 - (id)copyWithZone:(NSZone *)zone {     return self; } //retain返回单例本身 - (id)retain {     return self; } //引用计数总是为1 - (unsigned)retainCount {     return 1; } //release不做任何处理 - (void)release { } //autorelease返回单例本身 - (id)autorelease {     return self; } //真release私有接口 -(void)realRelease {       [super release]; } // -(void)dealloc {       //⋯⋯       printf("举例:在此处做一些单例结束时的收尾处理/n");        [super dealloc]; } @end //程序结束时析构静态c++类对象garbo， //在Garbo类的析构函数中释放instance struct Garbo {       ~Garbo(){[instance realRelease];} }; static Garbo garbo;