接收器（ <ViewController> ）没有带有标识符的关键字

Question

我不知道，并且尝试重命名故事板，清理项目，更换模拟器。 我不能凭空找工作。

我有一个从ViewController（A）到ViewController（B）的手动建模工具，称为“ MoveToLogin”。

发生的事情是，当您单击登录按钮时，我创建了一个自定义对象的新实例，该实例包含如下登录方法：

#ViewController.m
//If the username and password fields are not blank, attempt to log in.
        [_custom object loginUser:_usernameTxt.text password:_passwordTxt.text]

#custom object's login method (CustomObject.m)
-(void)loginUser:(NSString *)username password:(NSString *)password
{
    ViewController *viewcontroller = [[ViewController alloc]init];

    //Attempts to log in the user
    AFHTTPRequestOperationManager *manager = [AFHTTPRequestOperationManager manager];
    manager.requestSerializer = [AFHTTPRequestSerializer serializer];
    manager.responseSerializer = [AFJSONResponseSerializer serializer];
    NSDictionary *params = @ {@"username" : username, @"password": password};
    [manager POST:_login_url parameters:params
    success:^(AFHTTPRequestOperation *operation, id responseObject)
    {
        if([responseObject objectForKey:@"login_okay"])
        {
            _valid_login = YES;
            [viewcontroller onSuccessfulLogin];
        }
        else
        {
            _valid_login = NO;
            [viewcontroller onInvalidLogin];
        }
    }
          failure:
     ^(AFHTTPRequestOperation *operation, NSError *error) {
         [viewcontroller onRequestFail];
     }];
}

如您所见，自定义对象的方法显然在另一个类中，当从服务器接收到json响应时，调用ViewController（a）方法onSuccessfulLogin。

该方法如下所示：

-(void)onSuccessfulLogin
{
    //if we get a successful login
    [self performSegueWithIdentifier:@"MoveToLogin" sender:nil];
}

但是，每当我成功登录时，都会收到以下令人愉快的消息：

由于未捕获的异常'NSInvalidArgumentException'而终止应用程序，原因：'Receiver（）没有标识为'MoveToLogin'的segue

Answer 1

您不能像正在做的那样创建viewcontroller的实例。.通常，让异步方法使用块/委托是很好的。如何使用完成块来做类似的事情。

    #ViewController.m
    //If the username and password fields are not blank, attempt to log in.
     [_customobject  loginUser:@"" password:@"" completionBlock:^(BOOL validLogin, NSError *error) {
        if(error){
            [self onRequestFail];
        }else{
            if(validLogin){
                    //if we get a successful login
                 [self performSegueWithIdentifier:@"MoveToLogin" sender:nil];
            }else{
                //if we get a invalid login
            }
        }        
    }];

    #custom object's login method (CustomObject.m)
    -(void)loginUser:(NSString *)username password:(NSString *)password completionBlock:(void (^)(BOOL validLogin, NSError *error))completionblock{

        //Attempts to log in the user
        AFHTTPRequestOperationManager *manager = [AFHTTPRequestOperationManager manager];
        manager.requestSerializer = [AFHTTPRequestSerializer serializer];
        manager.responseSerializer = [AFJSONResponseSerializer serializer];
        NSDictionary *params = @ {@"username" : username, @"password": password};
        [manager POST:_login_url parameters:params
        success:^(AFHTTPRequestOperation *operation, id responseObject)
        {
            if([responseObject objectForKey:@"login_okay"])
            {
                _valid_login = YES;
                if (completionblock) completionblock(YES, nil);
            }
            else
            {
                _valid_login = NO;
                if (completionblock) completionblock(NO, nil);
            }
        }
              failure:^(AFHTTPRequestOperation *operation, NSError *error) {
             if (completionblock) completionblock(NO, error);
         }];
    }