一句话实现OC单例模式

// .h文件的实现#define SingletonH(methodName) + (instancetype)shared##methodName;// .m文件的实现#if __has_feature(objc_arc) // 是ARC#define SingletonM(methodName) /static id _instace = nil; /+ (id)allocWithZone:(struct _NSZone *)zone /{ /if (_instace == nil) { /static dispatch_once_t onceToken; /dispatch_once(&onceToken, ^{ /_instace = [super allocWithZone:zone]; /}); /} /return _instace; /} //- (id)init /{ /static dispatch_once_t onceToken; /dispatch_once(&onceToken, ^{ /_instace = [super init]; /}); /return _instace; /} //+ (instancetype)shared##methodName /{ /return [[self alloc] init]; /} /+ (id)copyWithZone:(struct _NSZone *)zone /{ /return _instace; /} //+ (id)mutableCopyWithZone:(struct _NSZone *)zone /{ /return _instace; /}#else // 不是ARC#define SingletonM(methodName) /static id _instace = nil; /+ (id)allocWithZone:(struct _NSZone *)zone /{ /if (_instace == nil) { /static dispatch_once_t onceToken; /dispatch_once(&onceToken, ^{ /_instace = [super allocWithZone:zone]; /}); /} /return _instace; /} //- (id)init /{ /static dispatch_once_t onceToken; /dispatch_once(&onceToken, ^{ /_instace = [super init]; /}); /return _instace; /} //+ (instancetype)shared##methodName /{ /return [[self alloc] init]; /} //- (oneway void)release /{ //} //- (id)retain /{ /return self; /} //- (NSUInteger)retainCount /{ /return 1; /} /+ (id)copyWithZone:(struct _NSZone *)zone /{ /    return _instace; /} / /+ (id)mutableCopyWithZone:(struct _NSZone *)zone /{ /    return _instace; /}#endif