单例模式通用宏

#define SingleH(name) + (instancetype)share##name;
//ARC
#if  __has_feature(objc_arc)
#define SingleM(name) static id _instance;\
+ (instancetype)allocWithZone:(struct _NSZone *)zone {\
    static dispatch_once_t onceToken;\
    dispatch_once(&onceToken, ^{\
        _instance = [super allocWithZone:zone];\
    });\
    return _instance;\
}\
\
+ (instancetype)share##name {\
    return [[self alloc] init];\
}\
\
- (id)copyWithZone:(NSZone *)zone {\
    return _instance;\
}\
\
- (id)mutableCopyWithZone:(NSZone *)zone {\
    return _instance;\
}

#else
//MRC
#define SingleM(name) static id _instance;\
+ (instancetype)allocWithZone:(struct _NSZone *)zone {\
static dispatch_once_t onceToken;\
dispatch_once(&onceToken, ^{\
_instance = [super allocWithZone:zone];\
});\
return _instance;\
}\
\
+ (instancetype)share##name {\
return [[self alloc] init];\
}\
\
- (id)copyWithZone:(NSZone *)zone {\
return _instance;\
}\
\
- (id)mutableCopyWithZone:(NSZone *)zone {\
return _instance;\
}\
- (oneway void)release {\
}\
- (instancetype)retain {\
    return _instance;\
}\
- (NSInteger)retainCount {\
    return MAXFLOAT;\
}

#endif