iOS协议里面可以定义成员变量和属性吗？
关注iOS开发：iOSDevTip
在CSDN上看到有人提的问题，觉得很有价值，先看代码：
@protocol CAMediaTiming /* The begin time of the object, in relation to its parent object, if * applicable. Defaults to 0. */ @property CFTimeInterval beginTime; /* The basic duration of the object. Defaults to 0. */ @property CFTimeInterval duration; /* The rate of the layer. Used to scale parent time to local time, e.g. * if rate is 2, local time progresses twice as fast as parent time. * Defaults to 1. */ @property float speed; /* Additional offset in active local time. i.e. to convert from parent * time tp to active local time t: t = (tp - begin) * speed + offset. * One use of this is to "pause" a layer by setting `speed' to zero and * `offset' to a suitable value. Defaults to 0. */ @property CFTimeInterval timeOffset; /* The repeat count of the object. May be fractional. Defaults to 0. */ @property float repeatCount; /* The repeat duration of the object. Defaults to 0. */ @property CFTimeInterval repeatDuration; /* When true, the object plays backwards after playing forwards. Defaults * to NO. */ @property BOOL autoreverses; /* Defines how the timed object behaves outside its active duration. * Local time may be clamped to either end of the active duration, or * the element may be removed from the presentation. The legal values * are `backwards', `forwards', `both' and `removed'. Defaults to * `removed'. */ @property(copy) NSString *fillMode; @end 问题：
上面那个协议时苹果自带的，为什么里面定义了成员变量呢？
网友回答：
这只是在头文件中声明，编译器是不会自动生成实例变量的，也就是说你可以用一个对象去实现这个协议，但是你不自己存储的话实例变量的话，访问同样会崩溃： self.fillModel = @“test”; // unrecognized selector
追问
你好，也就是说我需要这样：
@interface MyClass : NSObject < CAMediaTiming > @property CFTimeInterval beginTime; @end 这样才可以么？ 也就是@protocol能声明，不能定义变量么？
网友回答
协议声明出来的是方法，虽然看起来是属性，其实只有 getter、setter 这两个方法，内部是没有实例变量的，并且你不能去重定义它，只能在 getter、setter 里处理
正文到此结束
热门推荐
相关文章
近期评论
-
666
-
文章和留言都翻到11页了 没有OOM
-
-
朋友，翻页到11页，及以后，会出现OOM，无法访问
-
-
-
-
版本号是多少，你可以下载哪个代码仓库，jdk选1.8 直接跑就行
-
-
Loading...
![[HBLOG]公众号](https://www.liuhaihua.cn/img/qrcode_gzh.jpg)
