多线程篇----非ARC MVC 单例使用宏

// .h文件
#define HMSingletonH(name) + (instancetype)shared##name;

// .m文件
#define HMSingletonM(name) \
static id _instance; \
 \
+ (id)allocWithZone:(struct _NSZone *)zone \
{ \
    static dispatch_once_t onceToken; \
    dispatch_once(&onceToken, ^{ \
        _instance = [super allocWithZone:zone]; \
    }); \
    return _instance; \
} \
 \
+ (instancetype)shared##name \
{ \
    static dispatch_once_t onceToken; \
    dispatch_once(&onceToken, ^{ \
        _instance = [[self alloc] init]; \
    }); \
    return _instance; \
} \
 \
- (id)copyWithZone:(NSZone *)zone \
{ \
    return _instance; \
}  \
 \
- (oneway void)release { } \
- (id)retain { return self; } \
- (NSUInteger)retainCount { return 1;} \
- (id)autorelease { return self;}