只有文本字段中允许的日期

Question

我有一个alertview文本字段，用户应在其中输入日期。如何在此文本字段中指定仅允许dd / mm / yyyy的日期格式？我试图在不使用日期选择器的情况下实现这一目标。

到目前为止，我能够指定只允许使用数字和斜杠。这是我的代码：

if (buttonIndex != alertView.cancelButtonIndex)
        {

            UITextField *fieldDate = [alertView textFieldAtIndex:0];
            fieldDate.placeholder = @"Enter New Date";

            NSCharacterSet * setnew = [[NSCharacterSet characterSetWithCharactersInString:@"0123456789/"] invertedSet];

            if ([fieldDate.text rangeOfCharacterFromSet:setnew].location != NSNotFound)
            {

                //show alert view here
                UIAlertView *errorAlert1 = [[UIAlertView alloc] initWithTitle:@"Error" message:@"Only numbers and slashes are allowed in this field."delegate:self cancelButtonTitle:@"OK"otherButtonTitles:nil];
                [errorAlert1 show];

                FeeDate.text=@"00/00/0000";
            }
            else
            {

                FeeDate.text = fieldDate.text;
                [[NSUserDefaults standardUserDefaults] setObject:fieldDate.text forKey:DATE_KEY];
                [[NSUserDefaults standardUserDefaults] synchronize];
            }
        }