Cannot delete text in UITextField

Question

I have implemented a max character limit on a UITextField. The problem is that when input max number for characters, I am unable to backspace the characters. Can anyone tell me what I am doing wrong? Below is my code:

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

if (textField == pinCode) {
    if ([textField.text length]<=3) {
        return YES;        
    }
    else {
        return NO;
    }
}
else {
    return YES;
}
return YES;

}

Answer 1

Change the condition to:

if ([textField.text length]<=3 || string.length == 0) {
    ...

if the content of the string is control character f.e. backspace, the length will be zero