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QStackedWidget: How to check if the next widget should be shown

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  • H hobbyProgrammer
    21 Nov 2019, 11:36

    @JonB thank you.

        LoginWidget *login = qobject_cast<LoginWidget*>(ui->stackedWidget->widget(0));
    
        connect(login, SIGNAL(loginSuccesfull()), this, SLOT(showApp()));
    

    I currently get these errors (as loginSuccesfull is a public bool method):

    QObject::connect: No such signal LoginWidget::loginSuccesfull() in ..\stackedLogin\mainwindow.cpp:14
    QObject::connect:  (sender name:   'page')
    QObject::connect:  (receiver name: 'MainWindow')
    

    whenever I change loginSuccesfull() to a signal instead of public bool I get these errors:

    LNK2005:"public: bool _thiscall LoginWidget::loginSuccesfull(void)......" and LNK1169: one or more multiply defined symbols found

    J Offline
    J Offline
    J.Hilk
    Moderators
    wrote on 21 Nov 2019, 11:38 last edited by
    #11

    @hobbyProgrammer

    A Signal must not have a definition, only a declaration.

    The definition is made automatically in generated code by moc


    Be aware of the Qt Code of Conduct, when posting : https://forum.qt.io/topic/113070/qt-code-of-conduct


    Q: What's that?
    A: It's blue light.
    Q: What does it do?
    A: It turns blue.

    H 1 Reply Last reply 21 Nov 2019, 12:33
    3
    • H hobbyProgrammer
      21 Nov 2019, 11:36

      @JonB thank you.

          LoginWidget *login = qobject_cast<LoginWidget*>(ui->stackedWidget->widget(0));
      
          connect(login, SIGNAL(loginSuccesfull()), this, SLOT(showApp()));
      

      I currently get these errors (as loginSuccesfull is a public bool method):

      QObject::connect: No such signal LoginWidget::loginSuccesfull() in ..\stackedLogin\mainwindow.cpp:14
      QObject::connect:  (sender name:   'page')
      QObject::connect:  (receiver name: 'MainWindow')
      

      whenever I change loginSuccesfull() to a signal instead of public bool I get these errors:

      LNK2005:"public: bool _thiscall LoginWidget::loginSuccesfull(void)......" and LNK1169: one or more multiply defined symbols found

      J Offline
      J Offline
      JonB
      wrote on 21 Nov 2019, 11:41 last edited by
      #12

      @hobbyProgrammer
      In some shape or form you have not changed over the code to how signals/slots are declared and work in Qt. There are lots of example to read. You will need correct Qt declarations using signals & slots in your header files, and loginSuccesfull() won't be some bool function, it will emit the signal.

      I will leave others to help you with this, I don't even do Qt in C++.

      1 Reply Last reply
      0
      • J J.Hilk
        21 Nov 2019, 11:38

        @hobbyProgrammer

        A Signal must not have a definition, only a declaration.

        The definition is made automatically in generated code by moc

        H Offline
        H Offline
        hobbyProgrammer
        wrote on 21 Nov 2019, 12:33 last edited by
        #13

        @J-Hilk alright, but how would I check if the login is correct if there's no function definition?

        J J 2 Replies Last reply 21 Nov 2019, 12:36
        0
        • H hobbyProgrammer
          21 Nov 2019, 12:33

          @J-Hilk alright, but how would I check if the login is correct if there's no function definition?

          J Offline
          J Offline
          J.Hilk
          Moderators
          wrote on 21 Nov 2019, 12:36 last edited by J.Hilk
          #14

          @hobbyProgrammer

          the idea would be, that you emit the signal, as soon as your function verifies, that the login was successful !

          void LoginWidget::on_pushButton_clicked()
          {
                 QString username = ui->lineEdit_2->text();
                  QString password = ui->lineEdit->text();
              
                  if(username == "Test" && password == "Test123")
                  {
                       emit loginSuccessful();
                  }
          }
          

          Be aware of the Qt Code of Conduct, when posting : https://forum.qt.io/topic/113070/qt-code-of-conduct


          Q: What's that?
          A: It's blue light.
          Q: What does it do?
          A: It turns blue.

          1 Reply Last reply
          3
          • H hobbyProgrammer
            21 Nov 2019, 12:33

            @J-Hilk alright, but how would I check if the login is correct if there's no function definition?

            J Offline
            J Offline
            JonB
            wrote on 21 Nov 2019, 12:37 last edited by JonB
            #15

            @hobbyProgrammer
            Subject to @J-Hilk suggesting an alternative, as I wrote earlier retain your loginSuccesfull() as the slot for the pushbutton click. Have it emit a signal you define on successful validation of the widgets, the signal is a separate thing from your function which you must define as per the Qt/C++ rules.

            EDIT OK, @J-Hilk's code is the same thing, it's just that he has defined the pushbutton slot as on_pushButton_clicked() and the signal as logInSuccessful, so there is no longer any (non-signal) function named loginSuccesfull().

            H 1 Reply Last reply 21 Nov 2019, 12:53
            0
            • J JonB
              21 Nov 2019, 12:37

              @hobbyProgrammer
              Subject to @J-Hilk suggesting an alternative, as I wrote earlier retain your loginSuccesfull() as the slot for the pushbutton click. Have it emit a signal you define on successful validation of the widgets, the signal is a separate thing from your function which you must define as per the Qt/C++ rules.

              EDIT OK, @J-Hilk's code is the same thing, it's just that he has defined the pushbutton slot as on_pushButton_clicked() and the signal as logInSuccessful, so there is no longer any (non-signal) function named loginSuccesfull().

              H Offline
              H Offline
              hobbyProgrammer
              wrote on 21 Nov 2019, 12:53 last edited by
              #16

              @JonB alright, so using that code and these lines:

                  LoginWidget *login = qobject_cast<LoginWidget*>(ui->stackedWidget->widget(0));
                  connect(login, SIGNAL(loginSuccesfull()), this, SLOT(showApp()));
              

              should result in showApp to happen anytime the login was succesfull?

              J 1 Reply Last reply 21 Nov 2019, 13:04
              0
              • H hobbyProgrammer
                21 Nov 2019, 12:53

                @JonB alright, so using that code and these lines:

                    LoginWidget *login = qobject_cast<LoginWidget*>(ui->stackedWidget->widget(0));
                    connect(login, SIGNAL(loginSuccesfull()), this, SLOT(showApp()));
                

                should result in showApp to happen anytime the login was succesfull?

                J Offline
                J Offline
                JonB
                wrote on 21 Nov 2019, 13:04 last edited by
                #17

                @hobbyProgrammer
                I'm hoping so! Did you try it?

                H 1 Reply Last reply 21 Nov 2019, 13:09
                0
                • J JonB
                  21 Nov 2019, 13:04

                  @hobbyProgrammer
                  I'm hoping so! Did you try it?

                  H Offline
                  H Offline
                  hobbyProgrammer
                  wrote on 21 Nov 2019, 13:09 last edited by
                  #18

                  @JonB yes and it didn't work. I tried debugging but I can't seem to find what's going wrong. It hits the code where the emit loginSuccessfull() is set, but it doesn't go to the SLOT where it's connected to and it ends in :

                  while (!d->exit.loadAcquire())
                          processEvents(flags | WaitForMoreEvents | EventLoopExec);
                  
                  J 1 Reply Last reply 21 Nov 2019, 13:13
                  0
                  • H hobbyProgrammer
                    21 Nov 2019, 13:09

                    @JonB yes and it didn't work. I tried debugging but I can't seem to find what's going wrong. It hits the code where the emit loginSuccessfull() is set, but it doesn't go to the SLOT where it's connected to and it ends in :

                    while (!d->exit.loadAcquire())
                            processEvents(flags | WaitForMoreEvents | EventLoopExec);
                    
                    J Online
                    J Online
                    jsulm
                    Lifetime Qt Champion
                    wrote on 21 Nov 2019, 13:13 last edited by
                    #19

                    @hobbyProgrammer Did you make sure

                    connect(login, SIGNAL(loginSuccesfull()), this, SLOT(showApp()));
                    

                    succeeded? And is this "login" the one you're actually showing?

                    https://forum.qt.io/topic/113070/qt-code-of-conduct

                    H 1 Reply Last reply 21 Nov 2019, 13:18
                    1
                    • J jsulm
                      21 Nov 2019, 13:13

                      @hobbyProgrammer Did you make sure

                      connect(login, SIGNAL(loginSuccesfull()), this, SLOT(showApp()));
                      

                      succeeded? And is this "login" the one you're actually showing?

                      H Offline
                      H Offline
                      hobbyProgrammer
                      wrote on 21 Nov 2019, 13:18 last edited by
                      #20

                      @jsulm
                      it should be since I'm doing this:

                          LoginWidget *login = qobject_cast<LoginWidget*>(ui->stackedWidget->widget(0));
                      
                      J 1 Reply Last reply 21 Nov 2019, 13:19
                      0
                      • H hobbyProgrammer
                        21 Nov 2019, 13:18

                        @jsulm
                        it should be since I'm doing this:

                            LoginWidget *login = qobject_cast<LoginWidget*>(ui->stackedWidget->widget(0));
                        
                        J Online
                        J Online
                        jsulm
                        Lifetime Qt Champion
                        wrote on 21 Nov 2019, 13:19 last edited by
                        #21

                        @hobbyProgrammer And connect succeeded?

                        https://forum.qt.io/topic/113070/qt-code-of-conduct

                        H 1 Reply Last reply 21 Nov 2019, 13:24
                        1
                        • J jsulm
                          21 Nov 2019, 13:19

                          @hobbyProgrammer And connect succeeded?

                          H Offline
                          H Offline
                          hobbyProgrammer
                          wrote on 21 Nov 2019, 13:24 last edited by
                          #22

                          @jsulm I'm not sure, but I don't think so.

                          J 1 Reply Last reply 21 Nov 2019, 13:26
                          0
                          • H hobbyProgrammer
                            21 Nov 2019, 13:24

                            @jsulm I'm not sure, but I don't think so.

                            J Online
                            J Online
                            jsulm
                            Lifetime Qt Champion
                            wrote on 21 Nov 2019, 13:26 last edited by
                            #23

                            @hobbyProgrammer said in QStackedWidget: How to check if the next widget should be shown:

                            but I don't think so

                            Then it can't work.
                            Use new Qt5 connect syntax to be sure signal/slot are really connected:

                            connect(login, &LoginWidget::loginSuccesfull, this, &MainWindow::showApp);
                            

                            https://forum.qt.io/topic/113070/qt-code-of-conduct

                            H 1 Reply Last reply 21 Nov 2019, 13:27
                            2
                            • J jsulm
                              21 Nov 2019, 13:26

                              @hobbyProgrammer said in QStackedWidget: How to check if the next widget should be shown:

                              but I don't think so

                              Then it can't work.
                              Use new Qt5 connect syntax to be sure signal/slot are really connected:

                              connect(login, &LoginWidget::loginSuccesfull, this, &MainWindow::showApp);
                              
                              H Offline
                              H Offline
                              hobbyProgrammer
                              wrote on 21 Nov 2019, 13:27 last edited by
                              #24

                              @jsulm yes thank you. That worked!

                              Thank you so much for you patience and help.

                              1 Reply Last reply
                              0
                              • J Offline
                                J Offline
                                J.Hilk
                                Moderators
                                wrote on 21 Nov 2019, 13:27 last edited by
                                #25

                                Because this is getting out of hand:

                                https://github.com/DeiVadder/LoginExample


                                Be aware of the Qt Code of Conduct, when posting : https://forum.qt.io/topic/113070/qt-code-of-conduct


                                Q: What's that?
                                A: It's blue light.
                                Q: What does it do?
                                A: It turns blue.

                                1 Reply Last reply
                                4

                                20/25

                                21 Nov 2019, 13:18

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