iphone - 如何使用可选方法创建协议(protocol)？

Question

我注意到在 iPhone SDK 中定义的几个协议(protocol)中标记为可选的方法，例如 UIActionSheetDelegate 协议(protocol)。

如何定义自己的协议(protocol)，并将其中一些方法设置为可选？

Answer 1

来自“Formal Protocols”上的 Apple 页面:

Optional Protocol methods can be marked as optional using the @optional keyword. Corresponding to the @optional modal keyword, there is a @required keyword to formally denote the semantics of the default behavior. You can use @optional and @required to partition your protocol into sections as you see fit. If you do not specify any keyword, the default is @required.

@protocol MyProtocol

- (void)requiredMethod;

@optional
- (void)anOptionalMethod;
- (void)anotherOptionalMethod;

@required
- (void)anotherRequiredMethod;

@end