关于 UITextField的知识

1.规定输入内容的长度

//限制输入框中输入内容的长度
-(BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string{
    
    if (self.phoneNumTextField.text.length == 11) {
        if ([string isEqualToString:@""]) {
            return YES;
        }
        else {
            return NO;
        }
    }
    return YES;
}