ARC和MRC兼容的單例模式

2019-11-14 19:23:16

字體：大中小

來源：轉載

供稿：網友

一、ARC下的單例實現

　　說明：在用戶實例化的方法控制單次執行，同時開放單例的初始化方法。

-(instancetype)init{    self=[super init];    if(self){        static dispatch_once_t onceToken;        dispatch_once(&onceToken, ^{        });    }    return self;    }static id instance; +(instancetype)allocWithZone:(struct _NSZone *)zone{     static dispatch_once_t onceToken;    dispatch_once(&onceToken, ^{     instance=[super allocWithZone:zone];     }); return instance;}   + (instancetype) shareAudio{    static dispatch_once_t onceToken;    dispatch_once(&onceToken, ^{     instance=[[self alloc]init];     });     return instance; }  +(id)copyWithZone:(struct _NSZone *)zone{     return instance;}

二、MRC下的單例實現

　　說明：在用戶實例化的方法控制單次執行，同時開放單例的初始化方法,由于當前為MRC所以需要控制參內存管理的方法單次執行，因此相比ARC需要增加：

static id instance; +(instancetype)allocWithZone:(struct _NSZone *)zone{     static dispatch_once_t onceToken;     dispatch_once(&onceToken, ^{         instance=[super allocWithZone:zone];     });     return instance; }   + (instancetype) shareAudio{    static dispatch_once_t onceToken;     dispatch_once(&onceToken, ^{         instance=[[self alloc]init];     });     return instance; } -(oneway void)release{ }  -(instancetype)autorelease{     return instance; }  -(instancetype)retain{     return instance; }  -(NSUInteger)retainCount{     return 1; }

三、兼容MRC 和ARC的宏定義

　　說明：為了方便后期的引用，可以將單例抽取為宏定義，鑒于抽取的時候考慮到當前的手動計數和自動計數因此引入條件編譯：

#if !__has_feature(objc_arc)======當前是ARC#else======當前是MRC#endif代碼：#define singleton_h(name)  + (instancetype) share##name;#if !__has_feature(objc_arc)#define singleton_m(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{/    static dispatch_once_t onceToken;/    dispatch_once(&onceToken, ^{/        instance=[[self alloc]init];/    });/    return instance;/}/-(oneway void)release{/}//-(instancetype)autorelease{/    return instance;/}//-(instancetype)retain{/    return instance;/}//+(id)copyWithZone:(struct _NSZone *)zone{/    return instance;/}/-(NSUInteger)retainCount{/    return 1;/}#else#define singleton_m(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{/  static dispatch_once_t onceToken;/  dispatch_once(&onceToken, ^{/   instance=[[self alloc]init];/  });/  return instance;/}//+(id)copyWithZone:(struct _NSZone *)zone{/   return instance;/}#endif