#pragma mark - UITextFieldDelegate
- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string {

    NSString *toString = [textField.text stringByReplacingCharactersInRange:range withString:string];
    if (toString.length > 0) {
        // 保留規則: 小數點前9位，小數點後4位
 

        NSString *stringRegex = @"(\\+)?(([0]|(0[.]\\d{0,4}))|([1-9]\\d{0,8}(([.]\\d{0,4})?)))?";
        NSPredicate *predicate = [NSPredicate predicateWithFormat:@"SELF MATCHES %@", stringRegex];
        BOOL flag = [predicate evaluateWithObject:toString];
        if (!flag) {
            return NO;
        }
    }

    return
 
 YES;
}