代码如下，可直接拷贝到头文件中
#define singleton_h(name) +(instancetype)shared##name
# if __has_feature(objc_arc) //ARC #define singleton_m(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:(struct _NSZone *)zone\
{\
return _instance;\
}
#else //非ARC
#define singleton_m(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:(struct _NSZone *)zone\
{\
return _instance;\
}\
-(oneway void)release\
{\
\
}\
-(instancetype)autorelease\
{\
return _instance;\
}\
-(instancetype)retain\
{\
return _instance;\
}\
-(NSUInteger)retainCount\
{\
return ;\
} #endif
MRC要重写四个方法：
-(oneway void)release
{
}
-(instancetype)autorelease
{
return self;
}
-(instancetype)retain{
return self;
}
-(NSUInteger)retainCount{
return 1;
}