Question

I am currently restricting the user to write in a text from more than 4 character.

For this i am using this piece of code

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

    if ([textField.text length] == 4)
        return NO;
    else
        return YES;    
}

Its working fine and it do not allow the user to write more than 4 character.

But when i try to delete the existing character.The keyboard delete option is not working.

How to solve this problem

Answer 1

When shouldChangeCharactersInRange method is called text field still has an old value and so if its length is 4 you’re stuck. Better way to validate input will be to calculate what string you’re going to have in a field after the change and check if it is valid:

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString: (NSString *)string{
    NSString *newString = [textField.text stringByReplacingCharactersInRange:range
                                                         withString:string];
    return [newString length] <= 4;
}