How to check text field input at real time?

Question

I am writing validation for my textfield, I found something interesting that whether I can check how many digits I am typing into the textfield at real time. My text field i

Answer 1

Use UITextFieldDelegate. especially this function

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

and you can get sample codes links from here..