Using `textField:shouldChangeCharactersInRange:`,

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

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
}

Answer 2

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 3

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.

Answer 4

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 5

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

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

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
}