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;}