Objective-C传递方法作为参数 [英] Objective-C passing methods as parameters

问题描述

如何将一个方法作为参数传递给另一个方法？我在课堂上这样做。

How do you pass one method as a parameter to another method? I'm doing this across classes.

A类：

+ (void)theBigFunction:(?)func{
    // run the func here
}

B类：

- (void)littleBFunction {
    NSLog(@"classB little function");
}

// somewhere else in the class
[ClassA theBigFunction:littleBFunction]

C类：

- (void)littleCFunction {
    NSLog(@"classC little function");
}

// somewhere else in the class
[ClassA theBigFunction:littleCFunction]

推荐答案

你要找的类型是选择器（ SEL ），你得到一个方法的选择器这个：

The type you are looking for is selector (SEL) and you get a method's selector like this:

SEL littleSelector = @selector(littleMethod);

如果方法采用参数，你只需输入：他们去哪里，像这样：

If the method takes parameters, you just put : where they go, like this:

SEL littleSelector = @selector(littleMethodWithSomething:andSomethingElse:);

此外，方法不是真正的函数，它们用于向特定类发送消息（在开始时） +）或它的特定实例（以 - 开头）。函数是C类型，它没有像方法那样真正具有目标。

Also, methods are not really functions, they are used to send messages to specific class (when starting with +) or specific instance of it (when starting with -). Functions are C-type that doesn't really have a "target" like methods do.

一旦你得到一个选择器，你就可以在你的目标上调用该方法（无论如何）类或实例）像这样：

Once you get a selector, you call that method on your target (be it class or instance) like this:

[target performSelector:someSelector];

一个很好的例子是 UIControl ' s addTarget：action：forControlEvents：通常在以编程方式创建 UIButton 或其他控件对象时使用的方法。

A good example of this is UIControl's addTarget:action:forControlEvents: method you usually use when creating UIButton or some other control objects programmatically.

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