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;
}

Answer 2

Rather than test for whether the character is upper- or lower-case, just assume that it's lower case. Much simpler.

In the

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

method:

NSString *newString = [[textField.text stringByAppendingString:string] uppercaseString];
textField.text = newString;

return NO;

Answer 3

Maybe I haven't found all the kinks to this method, but so far it works well for me. It seems to avoid the issues with jumping selection to the end if you go down the route of returning NO from -textField:shouldChangeCharactersInRange:replacementString:. Since UITextField conforms to UIKeyInput, simply override the method -insertText: to change the input string to uppercase before calling super with the uppercase string:

- (void)insertText:(NSString *)text {
    NSString *uppercaseText = [text uppercaseString]
    [super insertText:uppercaseText]
}

Or if you've moved along to Swift:

override func insertText(text: String) {
    let uppercaseText = text.uppercaseString
    super.insertText(uppercaseText)
}

Answer 4

While all the other answers do actually work (they make the input uppercase), they all have the problem that the cursor position is not retained (try inserting a character in the middle of the existing text). This apparently happens in the setter of UITextField's text property, and I have not found a way to restore it programmatically (for example, restoring the original selectedTextRange does not work).

However, the good news is, that there is a direct way to replace parts of a UITextField's (or UITextView's) text, which does not suffer from this issue:

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string
{
    // not so easy to get an UITextRange from an NSRange...
    // thanks to Nicolas Bachschmidt (see http://stackoverflow.com/questions/9126709/create-uitextrange-from-nsrange)
    UITextPosition *beginning = textField.beginningOfDocument;
    UITextPosition *start = [textField positionFromPosition:beginning offset:range.location];
    UITextPosition *end = [textField positionFromPosition:start offset:range.length];
    UITextRange *textRange = [textField textRangeFromPosition:start toPosition:end];

    // replace the text in the range with the upper case version of the replacement string
    [textField replaceRange:textRange withText:[string uppercaseString]];

    // don't change the characters automatically
    return NO;
}

For further information on these methods, see the documentation of UITextInput.

Answer 5

To Automatically input uppercase in textfield:

Case 1: Add UITextDelegate protocol and implement the following method

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

    return NO;
}

Case 2:Set the following parameter in the ViewDidLoad() method in your view controller. Although in this case the user can turnoff the caps button on the keyboard.

urTextFieldName.autocapitalizationType = UITextAutocapitalizationTypeAllCharacters;

Answer 6

Set autocapitalizationType to UITextAutocapitalizationTypeAllCharacters on the UITextField.

See UITextInputTraits protocol (adopted by UITextField) for more details.