投放发件人参数 [英] Casting sender parameter

问题描述

我有一个方法接受发件人，并用UI按钮调用。如何让那个对象转换成UIImageView？基本上如何重新使用按钮的代码。

I have a method that accepts a sender and is called with a UIbutton. How do I get that object to casted into a UIImageView? Basically how do I re-use the code for the button.

- (IBAction)startClick:(id)sender { 
    button.animationImages = [NSArray arrayWithObjects:
                                       [UIImage imageNamed:@"Pic_1.png"],
                                       [UIImage imageNamed:@"Pic_2.png"],
                                       [UIImage imageNamed:@"Pic_3.png"],
                                       nil];
    [button setAnimationRepeatCount:1];
    button.animationDuration = 1;
    [button startAnimating];
}

推荐答案

我的第一个回应是可能是一个错误这样做。 UIButton 和 UIImageView 是 <$ c $的不同子类c> UIView （和 UIButton 是 UIControl ），所以他们只有共同的东西是 UIView 方法。如果 sender 确实是 UIButton ，将其视为 UIImageView 很可能会导致错误，例如无法识别的选择器发送到实例等。

My first response is that it's probably a mistake to do so. UIButton and UIImageView are distinct subclasses of UIView (and UIButton is a subclass of UIControl) so the only things they have in common are UIView methods. If sender is really a UIButton, treating it as a UIImageView is likely to result in errors, such as "unrecognized selector sent to instance" and the like.

一般来说，更清洁的解决方案是创建一个单独的方法对 UIImageView 的操作。 （与Java不同，Objective-C和Cocoa不喜欢将UI响应代码放到基于事件类型的单个方法中 - 而是基于需要发生的操作来逻辑组织代码。）

In general, a cleaner solution is to create a separate method that is the action for a UIImageView. (Unlike Java, Objective-C and Cocoa prefer to not shoehorn UI response code into a single method based on the event type — rather, you organize the code logically based on the operation that needs to happen.)

如果你必须从按钮和图像视图调用这个方法，你可以这样分离逻辑：

If you must call this method from both buttons and image views, you can separate the logic like this:

- (IBAction) startClick:(id)sender {
  if ([sender isKindOfClass:UIButton]) {
    ...
  }
  else if ([sender isKindOfClass:UIImageView]) {
    ...
  }
}

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