iPhone Force Textbox Input to Upper Case

Question

How do I force characters input into a textbox on the iPhone to upper case?

Answer 1

This solution is not fully satisfying.

Even with the autocapitalizationType set to UITextAutocapitalizationTypeAllCharacters, the user can still press caps to release the caps lock. And the textField.text = [textField.text stringByReplacingCharactersInRange:range withString:[string uppercaseString]]; return NO; solution is not that great: we loose the editing point if the user edits the middle of the text (after a textField.text =, the editing cursor goes to the end of the string).

I've done a mix of the two solution and here is what I propose: set UITextAutocapitalizationTypeAllCharacters, and add the following code to the delegate of the UITextField.

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range
replacementString:(NSString *)string {

    // Check if the added string contains lowercase characters.
    // If so, those characters are replaced by uppercase characters.
    // But this has the effect of losing the editing point
    // (only when trying to edit with lowercase characters),
    // because the text of the UITextField is modified.
    // That is why we only replace the text when this is really needed.
    NSRange lowercaseCharRange;
    lowercaseCharRange = [string rangeOfCharacterFromSet:[NSCharacterSet lowercaseLetterCharacterSet]];

    if (lowercaseCharRange.location != NSNotFound) {

        textField.text = [textField.text stringByReplacingCharactersInRange:range
                                                                 withString:[string uppercaseString]];
        return NO;
    }

    return YES;
}