使用`textField:shouldChangeCharactersInRange:`，如何获取包含当前输入字符的文本？

Question

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]];    
  }
}

However, the output I observe is that...

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

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

... when what I want is:

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

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

What am I doing wrong?

Answer 1

-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]];

Answer 2

-(BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string
{
    NSString * searchStr = [textField.text stringByReplacingCharactersInRange:range withString:string];

    NSLog(@"%@",searchStr);
    return YES;
}

Answer 3

Swift 3

Based on the accepted answer, the following should work in Swift 3 :

func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {

    let newString = NSString(string: textField.text!).replacingCharacters(in: range, with: string)

    return true
}

Note

Both String and NSString have methods called replacingCharacters:inRange:withString . However, as expected, the former expects an instance of Range , while the latter expects an instance of NSRange . The textField delegate method uses an NSRange instance, thus the use of NSString in this case.

Answer 4

不要使用 UITextFieldDelegate，而是尝试使用 UITextField 的“Editing Changed”事件。

Answer 5

In Swift(4), without NSString (pure Swift):

func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {

    if let textFieldString = textField.text, let swtRange = Range(range, in: textFieldString) {

        let fullString = textFieldString.replacingCharacters(in: swtRange, with: string)

        print("FullString: \(fullString)")
    }

    return true
}

As an extension:

extension UITextField {

    func fullTextWith(range: NSRange, replacementString: String) -> String? {

        if let fullSearchString = self.text, let swtRange = Range(range, in: fullSearchString) {

            return fullSearchString.replacingCharacters(in: swtRange, with: replacementString)
        }

        return nil
    }
}

// Usage:

func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {

    if let textFieldString = textField.fullTextWith(range: range, replacementString: string) {
        print("FullString: \(textFieldString)")
    }

    return true
}

Answer 6

Swift version for it :

func textField(textField: UITextField, shouldChangeCharactersInRange range: NSRange, replacementString string: String) -> Bool {

    if string == " " {
        return false
    }

    let userEnteredString = textField.text

    var newString = (userEnteredString! as NSString).stringByReplacingCharactersInRange(range, withString: string) as NSString

    print(newString)

    return true
}

Answer 7

This is the code you need,

if ([textField isEqual:self.textField1])
  textField2.text = [textField1.text stringByReplacingCharactersInRange:range withString:string];

Answer 8

use guard

func textField(textField: UITextField, shouldChangeCharactersInRange range: NSRange, replacementString string: String) -> Bool {
        guard case let textFieldString as NSString = textField.text where
            textFieldString.stringByReplacingCharactersInRange(range, withString: string).length <= maxLength else {
                return false
        }
        return true
    }

Answer 9

My solution is to use UITextFieldTextDidChangeNotification .

[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(copyText:) name:UITextFieldTextDidChangeNotification object:nil];

Don't forget to call [[NSNotificationCenter defaultCenter] removeObserver:self]; in dealloc method.

Answer 10

If you need to replace the textfield text with this you can use my solution (Swift 3): https://gist.github.com/Blackjacx/2198d86442ec9b9b05c0801f4e392047

After the replacement you can just get textField.text to retrieve the composed text.