Objective-C 协议
我在名为 TileOverlay.h 的文件中遇到了以下代码：
@protocol TileOverlay <MKOverlay>
我试图明确地理解它在做什么。然后，其他几个覆盖层会导入此 .h 文件。该文件本质上只是创建 MKOverlay 类的修改版本吗？
如果没有，您能解释一下它的作用吗？
I came across the following bit of code in a file called TileOverlay.h:
@protocol TileOverlay <MKOverlay>
I'm trying to understand explicitly what this is doing. Several other overlays then import this .h file. Does this file essentially just create a modified version of the MKOverlay class?
If not, can you please clarify what it does?
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这称为协议继承。
MKOverlay是一个协议，定义了一组供对象实现的方法。TileOverlay继承了MKOverlay，这意味着符合TileOverlay的对象应该实现MKOverlay中的方法和MKOverlay中的方法。 code>TileOverlay这里是一个链接这更多地讨论了协议继承
It's called protocol inheritance.
MKOverlayis a protocol, defining a set of methods for objects to implement.TileOverlayinherits forMKOverlay, meaning that an object conforming toTileOverlay, should implement methods fromMKOverlayand methods fromTileOverlayHere is a link that talks a little bit more about protocol inheritance
Objective-C 中的协议就是 Java 或 C# 中的接口。这是任何其他类都可以履行的契约，用 Obj-C 的说法符合。
这：
定义一个名为
TileOverlay的协议，该协议本身扩展了MKOverlay。也就是说，通过遵守TileOverlay，您还必须遵守MKOverlay。Obj-C 中的协议就像 Jave 或 C# 中的接口一样，与实现无关。它没有做任何事情。它只是编译时的一个标记，如果需要的话，可以在运行时检查某些功能是否存在。
A protocol in Objective-C is what you in Java or C# would call an interface. It is a contract that any other class can fulfill, in Obj-C parlance conform to.
This:
Defines a protocol named
TileOverlaythat in itself extendsMKOverlay. That is by conforming toTileOverlayyou must also conform toMKOverlay.Protocols in Obj-C, just as interfaces in Jave or C#, is not related to implementation. It does not do anything. It's just a marker at compile time, and at run-time if you want to, to check if some functionally exist.
MKOverlay是一个协议，TileOverlay是一个扩展MKOverlay的协议。任何符合
TileOverlay协议的类也都符合MKOverlay协议。请参阅 协议中的协议在文档中有详细的解释。
MKOverlayis a protocol, andTileOverlayis a protocol that extendsMKOverlay.Any class that conforms to the
TileOverlayprotocol also conforms to theMKOverlayprotocol.Refer to Protocols Within Protocols in the documentation for a detailed explanation.
您可以将协议想象为 Java 或 C# 中的接口，基本上它们声明了实现类必须遵循的契约。不同之处在于，在 Objective C 中，您可以将某些声明的方法设为可选。
You can think of protocols like interfaces in Java or C#, basically they declare a contract that the implementing classes must follow. The difference is that in Objective C you can make some of the declared methods optional.