Objective C协议与Java接口相同？ [英] Objective C protocol as an equal to Java Interface?

问题描述

问题不仅在于标题，而在于我将如何实现这一点，而不是试图将Java / Flash设计强制转换为Objective C（iPhone）程序。

The question is not only regarding the headline, but more of a "how will I achieve this, without trying to force a Java/Flash design into an Objective C (iPhone)program".

我有6个视图扩展了UIView，这些视图都有不同的行为，但共享某些方法，如 - （void）update 和 - （void）changeState：（NSInteger）state 。

I have 6 views that extends UIView, these views all have different behavior but share certain methods, like -(void) update and -(void) changeState:(NSInteger)state.

一个viewController，它的工作是更新，实例化和显示这些视图有一个开关块来做这件事。所以switch（4）{...}实例化UIView4，但因为我需要对当前实例化视图的引用（要做 update 和 changeState： ），我的ViewController上有一个名为self.currentView的UIView属性。当实例化的UIView4扩展UIView时，我可以轻松地去 [self.currentView addSubview：UIView4instance] 然后释放UIView4instance。

A viewController, whose job is it to update, instantiate and display these views has a switch block to do this. So switch(4) {...} instantiates UIView4, but as I need a reference to the currently instantiated view (to do update and changeState:), I have a UIView property on my ViewController called self.currentView. As the instantiated UIView4 extends UIView I can easily go [self.currentView addSubview:UIView4instance] and then release the UIView4instance.

现在如何在视图上调用 [UIView4instance update] 方法？或者 [UIView5instance changeState] 等等。
因为我把它添加到 self.currentView 这是类型UIView它不再有任何理由相信它有更新或 changeState：方法，这意味着我无法迭代视图并向他们发送这些消息。

Now how will I call the [UIView4instance update] method on the view? or the [UIView5instance changeState] etc. etc. Since I added it to self.currentView which is of type UIView it no longer has any reason to believe it has an update or changeState: method, meaning I cannot iterate the views and send them these messages.

这种方法带来了大量其他问题，每次我需要进行任何操作时，我都需要测试并键入我的视图在他们。

This approach brings on a ton of other problems, I would need to test and typeCast my views each time I needed to do any operations on them.

如果我在Java中使用这种复合模式方法。我要么编写一个所有视图（UIView1，UIview2 ...... UIViewN）都会实现的接口。或者也许是一个抽象类，所有视图都继承了 changeState：和更新方法。

If I were doing something like this Composite Pattern approach in, say, Java. I would either write an interface that all the views (UIView1, UIview2.... UIViewN) would implement. Or maybe an abstract class that all the views inherited the changeState: and update methods from.

这样我就可以 self.currentView 只知道我在视图中添加对象，它们都符合这些方法。

This way I could have self.currentView just know that I'm adding objects to your view and they all conform to these methods.

我能想到的两个解决方案，我的Objective-C经验非常小：
使用委托或类别来做这件事，但这似乎有点过分杀戮：/
我想我也可以扩展UIView然后扩展我的类再次扩展UIView，但是可能有一个原因Objective-C不直接支持抽象类......

The two solutions I can think of, with my very small Objective-C experience is: doing it with delegation or categories, but this seems overkill in every way :/ I guess I could also extend UIView and then extend my class extending UIView again, but there is probably a reason Objective-C does not directly support abstract classes...

希望有人能指出我在这些问题上的正确方向。
谢谢：）

Hope someone could point me in the right direction regarding these issues. Thanks:)

推荐答案

是的，它是平等的。你可以声明一个协议

Yes it is equal. You can declare a protocol

@protocol MyViewProtocol
-(void)update;
-(void)changeState:(NSInteger)state;
@end

并声明您的子类

@interface MyUIView3 : UIView<MyViewProtocol> {
....
}
....
@end

然后，声明

UIView<MyViewProtocol>* view=[[MyUIView3 alloc] init];

表示 view 是一个实例（属于 UIView 的子类，它也符合 MyViewProtocol 。
我认为就像它在Java中的工作方式一样。请参阅协议上的Apple doc 。

means that view is an instance (of a subclass of) UIView which also conforms to MyViewProtocol. Just the way it works in Java, I think. See the apple doc on protocols.

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