使用`textField：shouldChangeCharactersInRange：`，如何获取包含当前类型字符的文本？ [英] Using `textField:shouldChangeCharactersInRange:`, how do I get the text including the current typed character?

问题描述

我正在使用下面的代码尝试让 textField2 的文本内容更新以匹配 textField1 只要用户键入 textField1 。

I'm using the code below to try and have textField2's text content get updated to match textField1's whenever the user types in textField1.

- (BOOL) textField: (UITextField *)theTextField shouldChangeCharactersInRange: (NSRange)range replacementString: (NSString *)string {    
  if (theTextField == textField1){    
     [textField2 setText:[textField1 text]];    
  }
}

然而，我观察到的输出是......

However, the output I observe is that...

textField2为12，当textField1为123时

textField2 is "12", when textField1 is "123"

textField2是123，当textField1是1234

textField2 is "123", when textField1 is "1234"

...当我想要的是：

... when what I want is:

textField2为123，当textField1为123时

textField2 is "123", when textField1 is "123"

textField2为1234，当textField1是1234

textField2 is "1234", when textField1 is "1234"

我做错了什么？

推荐答案

-shouldChangeCharactersInRange 在文本字段实际更改其文本之前调用，这就是您获取旧文本值的原因。要在更新后使用文本：

-shouldChangeCharactersInRange gets called before text field actually changes its text, that's why you're getting old text value. To get the text after update use:

[textField2 setText:[textField1.text stringByReplacingCharactersInRange:range withString:string]];

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