How to stop entering value in UITextField

How to stop entering value in UITextField if t开发者_如何学Gohe length is greater then 20 char.

Programmatically.

try this

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string 
{
    //Set tag for a textfield
    if(textField.tag==10)
    {
        NSUInteger newLength = [textField.text length] + [string length] - range.length;
        return (newLength > 20) ? NO : YES;

    }
}

Set the maximum character length of a UITextField