iphone - 错误：应用程序委托加载是未声明的标识符

Question

我在 iPhone 注册页面编码中遇到了意外问题。错误是

应用程序委托加载是未声明的标识符

   if (!isValid)
   {
      [AppDelegate showAlert:@"Alert!" withMessage:strMessage];
   }
   return isValid;
}

-(void)registerUser {
   [Loading startLoading:YES];

   NSString *urlString = [NSString stringWithFormat:@"url=%@",Access_Token];
   //firstname,lastname,email,username,password

   NSString *parameter = [NSString   
        stringWithFormat:@"firstname=%@&lastname=%@&email=%@&username=%@&password=%@",
        firstnameField.text,lastnameField.text,
        emailField.text,UsernameField.text,passwordField.text];

   NSConnection *conn = [[NSConnection alloc] initWithDelegate:self];
   [conn sendRequest:urlString withParaMeter:parameter withMethod:@"POST" withTag:1];
   [conn startAsynchronousRequest];
}