Objective-C中的选择器只是向对象发送消息的另一种方式吗? [英] Are selectors in Objective-C just another way to send a message to an object?

问题描述

Objective-C中的选择器是否只是向对象发送消息的另一种方式?我真的不明白为什么或如何使用它们.

Are selectors in Objective-C just another way to send a message to an object? I really don't understand why or how to use them.

推荐答案

它们不是向对象发送消息的另一种方法，它们是唯一的方法.例如，在[myView setValue:@"foo"]中，setValue:是选择器. (另一种不太方便的写相同方法的方法是objc_msgSend(myView, @selector(setValue:), @"foo").)

They aren’t another way to send a message to an object, they’re the only way. For example, in [myView setValue:@"foo"], setValue: is a selector. (Another, less convenient way of writing the same thing is objc_msgSend(myView, @selector(setValue:), @"foo").)

正如伊恩·亨利(Ian Henry)所说，您可以使用SEL值在运行时而不是编译时选择选择器.这是可可粉中的一项基本技术.用户界面通常使用目标/动作绑定连接到控制器，其中目标是对象，而动作是选择器.通常，您可以在笔尖中进行设置，但是也可以通过代码进行设置:

As Ian Henry says, you can use SEL values to choose a selector at runtime instead of compile time. This is a fundamental technique in Cocoa; user interfaces are generally connected to controllers using target/action bindings, where the target is an object and the action is a selector. Normally you set this up in a nib, but you can also do it in code:

[myButton setTarget:myController];
[myButton setAction:@selector(buttonClicked:)]; // Clicking the button will now call [myController buttonClick:myButton].

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