// .h

#define singleton_interface(class) + (instancetype)shared##class;

// .m

#define singleton_implementation(class) \

static class *_instance; \

\

+ (id)allocWithZone:(struct _NSZone *)zone \

{ \

static dispatch_once_t onceToken; \

dispatch_once(&onceToken, ^{ \

_instance = [super allocWithZone:zone]; \

}); \

\

return _instance; \

} \

\

+ (instancetype)shared##class \

{ \

if (_instance == nil) { \

_instance = [[class alloc] init]; \

} \

\

return _instance; \

}