创建线程安全的单例（ARC或 非ARC）

一：创建 宏 文件 SynthesizeSingleton.h

?

SynthesizeSingleton.h

 

#if __has_feature(objc_arc) // ARC Version

 

#define SYNTHESIZE_SINGLETON_FOR_CLASS(classname)   \

\

+ (classname *)shared##classname\

{\

    static classname *shared##classname = nil;\

    static dispatch_once_t onceToken;\

    dispatch_once(&onceToken, ^{\

        shared##classname = [[classname alloc] init];\

    });\

    return shared##classname;\

}

 

#else // Non-ARC Version

 

#define SYNTHESIZE_SINGLETON_FOR_CLASS(classname) \

static classname *shared##classname = nil; \

+ (classname *)shared##classname \

{ \

    @synchronized(self) \

    { \

        if (shared##classname == nil) \

        { \

            shared##classname = [[self alloc] init]; \

        } \

    } \

    return shared##classname; \

} \

\

+ (id)allocWithZone:(NSZone *)zone \

{ \

@synchronized(self) \

{ \

if (shared##classname == nil) \

{ \

shared##classname = [super allocWithZone:zone]; \

return shared##classname; \

} \

} \

return nil; \

} \

- (id)copyWithZone:(NSZone *)zone \

{ \

return self; \

} \

- (id)retain \

{ \

return self; \

} \

- (NSUInteger)retainCount \

{ \

return NSUIntegerMax; \

} \

- (oneway void)release \

{ \

} \

- (id)autorelease \

{ \

return self; \

}

 

#endif

　　二：使用

?

MyClass.h

 

@interface MyClass : NSObject

 

+(DataStorage *)sharedMyClass;

 

@end

MyClass.m

 

#import "SynthesizeSingleton.h"

@implementation MyClass

SYNTHESIZE_SINGLETON_FOR_CLASS(MyClass)

@end

　参考资料