目标 C：什么是“(id)发件人”？

发布于 2024-10-30 13:55:34 字数 153 浏览 6 评论 0 原文

在一些IBAction中我看到：

- (IBAction)pushButton:(id)sender;

This (id)sender when do I use it?

原文

In some IBAction I saw:

- (IBAction)pushButton:(id)sender;

This (id)sender when do I use it?

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帝王念 2024-11-06 13:55:34

Matt Galloway 描述了 (id) 的含义发送者在 iPhone Dev SDK 论坛上的操作如下：

(id)sender 是将消息发送到该选择器的对象。就像在委托函数中，您可以将控制传递给函数等。

如果您有 2 个对象正在调用该选择器并且您想要区分它们，则可以使用此选项。当然，您可以只使用两个不同的函数，但使用一个函数通常更干净且代码重复更少。

请参阅
UIControl 类参考了解更多信息细节。

举个例子，UITextField 有一个委托，它在 UITextField 编辑结束时触发：

-(IBAction) editingEnded:(id) sender {
   // the cast goes here, lets assume there's more than one UITextfield 
   // in this Owner and you want to know which one of them has triggered
   // the "editingEnded" delegate
   UITextField *textField= (UITextField*)sender;
   if(textField == iAmTheLastTextField)
   {
     // for example login now.
     [self login];
   }
}

Matt Galloway described the meaning of (id) sender in actions on the iPhone Dev SDK forums thusly:

(id)sender is the object which sent the message to that selector. It's like in the delegate functions where you have the control passed in to the function, etc.

You'd use this if you had 2 objects which were calling that selector and you wanted to distinguish between them. Of course, you could just use two different functions, but it's often cleaner and less duplication of code to use one function.

See the
UIControl Class Reference for more details.

An example for that, UITextField has a delegate which triggers when the UITextField editing ends:

-(IBAction) editingEnded:(id) sender {
   // the cast goes here, lets assume there's more than one UITextfield 
   // in this Owner and you want to know which one of them has triggered
   // the "editingEnded" delegate
   UITextField *textField= (UITextField*)sender;
   if(textField == iAmTheLastTextField)
   {
     // for example login now.
     [self login];
   }
}

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美胚控场 2024-11-06 13:55:34

(id)sender is the object which sent the message to that selector.

代码示例：

- (IBAction)submitButton:(id)sender {
    UIButton *button = (UIButton *)sender;
    [button setEnabled:NO];
    [button setTitle:@"foo" forState:UIControlStateDisabled];
}

(id)sender is the object which sent the message to that selector.

Code example:

- (IBAction)submitButton:(id)sender {
    UIButton *button = (UIButton *)sender;
    [button setEnabled:NO];
    [button setTitle:@"foo" forState:UIControlStateDisabled];
}

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