单例设计模式
- 单例设计模式：让类的对象称为系统中唯一的实例
- 想要实现单例的类，必须遵守NSCopying和NSMutableCopying协议
- 重写allocWithZone:方法
- 重写copyWithZone:方法
- 重写mutableCopyWithZone:方法
- 提供访问单例的方法shareSoundTool
- MRC还需要重写其他的方法
static SoundTool *_instance = nil;
+ (instancetype)shareSoundTool
{
SoundTool *instance = [[self alloc] init];
return instance;
}
+ (instancetype)allocWithZone:(struct _NSZone *)zone
{
static dispatch_once_t onceToken;
dispatch_once(&onceToken, ^{
_instance = [[super allocWithZone:zone] init];
});
return _instance;
}
- (id)copyWithZone:(NSZone *)zone{
return _instance;
}
- (id)mutableCopyWithZone:(NSZone *)zone
{
return _instance;
}
// MRC
#if !__has_feature(objc_arc)
- (oneway void)release
{
}
- (instancetype)retain
{
return _instance;
}
- (NSUInteger)retainCount
{
return MAXFLOAT;
}
- (instancetype)autorelease
{
return self;
}
#endif
单例可以定义成宏
// .h文件中方法声明
#define interfaceSingleton(name) +(instancetype)share##name
// .m文件中方法实现
#if __has_feature(objc_arc)
// ARC
#define implementationSingleton(name) \
static name *_instance = nil; \
+ (instancetype)share##name \
{ \
name *instance = [[self alloc] init]; \
return instance; \
} \
+ (instancetype)allocWithZone:(struct _NSZone *)zone \
{ \
static dispatch_once_t onceToken; \
dispatch_once(&onceToken, ^{ \
_instance = [[super allocWithZone:zone] init]; \
}); \
return _instance; \
} \
- (id)copyWithZone:(NSZone *)zone{ \
return _instance; \
} \
- (id)mutableCopyWithZone:(NSZone *)zone \
{ \
return _instance; \
}
#else
// MRC
#define implementationSingleton(name) \
static name *_instance = nil; \
+ (instancetype)share##name \
{ \
name *instance = [[self alloc] init]; \
return instance; \
} \
+ (instancetype)allocWithZone:(struct _NSZone *)zone \
{ \
static dispatch_once_t onceToken; \
dispatch_once(&onceToken, ^{ \
_instance = [[super allocWithZone:zone] init]; \
}); \
return _instance; \
} \
- (id)copyWithZone:(NSZone *)zone{ \
return _instance; \
} \
- (id)mutableCopyWithZone:(NSZone *)zone \
{ \
return _instance; \
} \
- (oneway void)release \
{ \
} \
- (instancetype)retain \
{ \
return _instance; \
} \
- (NSUInteger)retainCount \
{ \
return MAXFLOAT; \
}\
- (instancetype)autorelease\
{\
return self;\
}
#endif
