Using 'Textfield:Shouldchangecharactersinrange:', How to Get the Text Including the Current Typed Character

Using `textField:shouldChangeCharactersInRange:`, how do I get the text including the current typed character?

-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]];

How shouldChangeCharactersInRange works in Swift?

Swift 4, Swift 5

This method doesn't use NSString

// MARK: - UITextFieldDelegate

extension MyViewController: UITextFieldDelegate {
    func textField(_ textField: UITextField,
                   shouldChangeCharactersIn range: NSRange,
                   replacementString string: String) -> Bool {
        if let text = textField.text,
           let textRange = Range(range, in: text) {
           let updatedText = text.replacingCharacters(in: textRange,
                                                       with: string)
           myvalidator(text: updatedText)
        }
        return true
    }
}

Note. Be careful when you use a secured text field.

Textfield shouldchangecharactersinrange swift

You could use a target on your textField with the control event EditingChanged instead of the delegate method.

Swift >= 1.0

myTextField.addTarget(self, action: "didChangeText:", forControlEvents: .EditingChanged)

Swift 3.0 (String literal selectors are deprecated, use #selector)

myTextField.addTarget(self, action: #selector(didChangeText(_:)), for: .editingChanged)

Then use the targeted method to run your checks.

func didChangeText(textField:UITextField) {
    if textField.text == "apple" {
        checkImageView1.hidden = false
    } else {
        checkImageView1.hidden = true
    }
}

Limiting characters and character length in textField(_:shouldChangeCharactersInRange:replacementString:)

Try this:

func textField(textField: UITextField, shouldChangeCharactersInRange range: NSRange, replacementString string: String) -> Bool {
    if textField == usernameField, let text = textField.text {
        let newLength = text.characters.count + string.characters.count - range.length
        return newLength <= 48 && !string.containsString("|")
    }

    return true
}

UITextField - Add a character/s after 1st character is entered while typing

-shouldChangeCharactersInRange gets called before the change to the text field takes place, so the length is still 0 (see Using `textField:shouldChangeCharactersInRange:`, how do I get the text including the current typed character?). Try this instead:

- (BOOL)textField:(UITextField*)textField shouldChangeCharactersInRange:(NSRange)range
replacementString: (NSString*) string {
    if (textField == currHeight) {
        NSString *text = [textField.text stringByReplacingCharactersInRange:range
        withString: string];
        if (text.length == 1) { //or probably better, check if int
            textField.text = [NSString stringWithFormat: @"%@ ft ", text];
            return NO;
        }
    }
    return YES;
}  

Make portion of UITextView undeletable

sch's last edit makes a decent answer, but I want to offer a slightly more flexible approach.

You have to keep in mind the copy/paste system. User might select all the text in text field and try to paste in the entire value which might be perfectly acceptable, but if (range.location <= 9) { return NO; } will reject it. The way I'd do it is put together a string that would be a result of successful edit and then check if that string would start with your desired prefix.

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string
{
    NSString *resultString = [textField.text stringByReplacingCharactersInRange:range withString:string];
    NSLog(@"resulting string would be: %@", resultString);
    NSString *prefixString = @"blabla";
    NSRange prefixStringRange = [resultString rangeOfString:prefixString];
    if (prefixStringRange.location == 0) {
        // prefix found at the beginning of result string
        return YES;
    }
    return NO;
}

Edit: if you want to check if the current string in text field starts with the prefix, you can use rangeOfString: the same way:

NSRange prefixRange = [textField.text rangeOfString:prefixString];
if (prefixRange.location == 0) {
    // prefix found at the beginning of text field
}

is it possible to know if user is typing or deleting characters in a textfield?

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string
{
    if (range.length > 0)
    {
         // We're deleting
    }
    else
    {
        // We're adding
    }
}

How do I get the value of a UITextfield as characters are being typed in real time?

Try this:

 func textField(textField: UITextField, shouldChangeCharactersInRange range: NSRange, replacementString string: String) -> Bool {
        let invalidCharacters = NSCharacterSet(charactersInString: "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890_").invertedSet
        if let range = string.rangeOfCharacterFromSet(invalidCharacters, options: nil, range:Range<String.Index>(start: string.startIndex, end: string.endIndex)) {
            return false
        }

        return true
    }

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