从带有参数的方法名称创建选择器

问题描述

我有一个代码示例，可从当前对象

I have a code sample that gets a SEL from the current object,

SEL callback = @selector(mymethod:parameter2);

我有一个类似

 -(void)mymethod:(id)v1 parameter2;(NSString*)v2 {
}

现在我需要将mymethod移动到另一个对象，例如myDelegate.

Now I need to move mymethod to another object, say myDelegate.

我尝试过:

SEL callback = @selector(myDelegate, mymethod:parameter2);

但是不会编译.

推荐答案

SEL是表示Objective-C中选择器的一种类型. @selector()关键字返回您描述的SEL.它不是函数指针，您不能将任何对象或任何类型的引用传递给它.对于选择器中的每个变量(方法)，必须在对@selector的调用中表示该变量.例如:

SEL is a type that represents a selector in Objective-C. The @selector() keyword returns a SEL that you describe. It's not a function pointer and you can't pass it any objects or references of any kind. For each variable in the selector (method), you have to represent that in the call to @selector. For example:

-(void)methodWithNoParameters;
SEL noParameterSelector = @selector(methodWithNoParameters);

-(void)methodWithOneParameter:(id)parameter;
SEL oneParameterSelector = @selector(methodWithOneParameter:); // notice the colon here

-(void)methodWIthTwoParameters:(id)parameterOne and:(id)parameterTwo;
SEL twoParameterSelector = @selector(methodWithTwoParameters:and:); // notice the parameter names are omitted

选择器通常传递给委托方法和回调，以指定在回调期间应在特定对象上调用哪个方法.例如，当您创建计时器时，回调方法专门定义为:

Selectors are generally passed to delegate methods and to callbacks to specify which method should be called on a specific object during a callback. For instance, when you create a timer, the callback method is specifically defined as:

-(void)someMethod:(NSTimer*)timer;

因此，当您安排计时器时，您将使用@selector来指定对象上的哪个方法实际上将负责回调:

So when you schedule the timer you would use @selector to specify which method on your object will actually be responsible for the callback:

@implementation MyObject

-(void)myTimerCallback:(NSTimer*)timer
{
    // do some computations
    if( timerShouldEnd ) {
      [timer invalidate];
    }
}

@end

// ...

int main(int argc, const char **argv)
{
    // do setup stuff
    MyObject* obj = [[MyObject alloc] init];
    SEL mySelector = @selector(myTimerCallback:);
    [NSTimer scheduledTimerWithTimeInterval:30.0 target:obj selector:mySelector userInfo:nil repeats:YES];
    // do some tear-down
    return 0;
}

在这种情况下，您指定每30秒用myTimerCallback向对象obj发送消息.

In this case you are specifying that the object obj be messaged with myTimerCallback every 30 seconds.

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