ios开发知识小集-宏

// .h文件的实现
// .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; 
}