How can I force a UITextField to only support lowercase characters?

Question

I want to override the key pressed event to force that, even when a capital key is pressed, the resulting output is still lowercase.

Orn Arnarson · Accepted Answer · 2015-07-01T22:41:37.190

This should work (you should also set textfield.autocapitalizationType=UITextAutocapitalizationTypeNone)

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string {
    if (textField==_usernameTextfield || textField==_emailTextfield) {
        NSRange lowercaseCharRange;
        lowercaseCharRange = [string rangeOfCharacterFromSet:[NSCharacterSet uppercaseLetterCharacterSet]];

        if (lowercaseCharRange.location != NSNotFound) {
            // some uppercase chars where found, need to replace

            UITextPosition *beginning = textField.beginningOfDocument;
            UITextPosition *start = [textField positionFromPosition:beginning offset:range.location];
            // new cursor location after insert/paste/typing
            NSInteger cursorOffset = [textField offsetFromPosition:beginning toPosition:start] + string.length;

            // convert whole text to lowercase and update the textfield
            textField.text = [textField.text stringByReplacingCharactersInRange:range
                                                                 withString:[string lowercaseString]];

            // now reposition the cursor
            UITextPosition *newCursorPosition = [textField positionFromPosition:textField.beginningOfDocument offset:cursorOffset];
            UITextRange *newSelectedRange = [textField textRangeFromPosition:newCursorPosition toPosition:newCursorPosition];
            [textField setSelectedTextRange:newSelectedRange];
            return NO;
        }
    }
    return YES;
}

i upvoted ur answer. but you should check this accepted Answer http://stackoverflow.com/questions/21092182/uppercase-characters-in-uitextfield . you just need to textField.text = [textField.text stringByReplacingCharactersInRange:range withString:[string lowercaseString]]; and return NO; — Vatsal Shukla, May 20 '16 at 07:21

brandonscript · Answer 2 · 2016-01-29T17:05:59.433

4

Solution is to add a selector for textFieldDidChange:

[self addTarget:self
                  action:@selector(textFieldDidChange:)
        forControlEvents:UIControlEventEditingChanged];

And in the textFieldDidChange event, add the following:

- (void)textFieldDidChange:(UITextField*)textField {
    textField.text = [textField.text lowercaseString];
}

Or you can use the Interface Builder @IBAction Editing Changed

Swift 2 version:

@IBAction func textChanged(sender: UITextField) {
    sender.text = sender.text?.lowercaseString
}

edited Jan 29 '16 at 17:05

answered Sep 18 '14 at 01:22

brandonscript

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This is not the best approach. It would be better to implement the `textField:shouldChangeCharactersInRange:replacementString:` method and update each change as it happens. – rmaddy Sep 18 '14 at 01:42
That only fires after the text appears in the box though, not pleasant UX. – brandonscript Sep 18 '14 at 01:43
My approach actually forces the lowercase as the user types. – rmaddy Sep 18 '14 at 02:02
Weird.. I was doing that before returning the BOOL and it wasn't updating. Post an answer if you like. – brandonscript Sep 18 '14 at 02:05
If you explicitly modify the text field in the `textField:shouldChangeCharactersInRange:replacementString:`, return `NO`. – rmaddy Sep 18 '14 at 02:18
1

The problem with this approach is that if the user enters a character in the middle of the text, it jumps the selection point to the end of the text. – matt Oct 02 '17 at 00:31

How can I force a UITextField to only support lowercase characters?

2 Answers2