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  4. How do I make a custom parent class from a class that inherits from QMainWindow?
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How do I make a custom parent class from a class that inherits from QMainWindow?

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  • mrjjM mrjj

    Hi
    You can use lambdas to have "slots" in main
    https://artandlogic.com/2013/09/qt-5-and-c11-lambdas-are-your-friend/
    (in place )

    Or just create a QObject based helper class to hold the slots. So you connect say
    ServiceAppLayout something to helpers object something.

    • Can you add connections programmatically?
      Yes! just use connect statement.
      connect( pointer to instance, signal, pointer to instance, slot )
      Best to use new syntax.
      http://wiki.qt.io/New_Signal_Slot_Syntax

    Im still not 100% i understand you issue. :)
    can you show a line where u need "this" in main to help me understand the actual issue.

    G Offline
    G Offline
    graniteDev
    wrote on last edited by graniteDev
    #6

    @mrjj hmm....maybe it's not as big of an issue, more my trying to do it the hardway ignorantly. I gave thought to a helper class, but only fleetingly thinking that was the incorrect way of doing it in an object oriented paradigm.

    Although I'm still not sure even adding a menu item with a helper class is possible.
    Normally to set up a menu item the code looks like this:

        utilMenu = menuBar()->addMenu("Utilities");
    
        // utilites menu list
        QAction *networkAction = new QAction("Network",this);
    
        networkAction->setCheckable(false);
    
        utilMenu->addAction(networkAction);
        utilMenu->addSeparator();
    
        connect(networkAction, &QAction::triggered, this, &ServiceAppLayout::onNetworkAction);
    

    and I tried, I can't access utilMenu->addAction from main.cpp even though I made utilMenu
    public.

    w.utilMenu.
    

    Nothing would come up after the "." like normal so I realized something isn't quite right and I can't access those members.

    I take it actually inheriting a class with a custom ui is impossible?

    mrjjM 1 Reply Last reply
    0
    • G graniteDev

      @mrjj hmm....maybe it's not as big of an issue, more my trying to do it the hardway ignorantly. I gave thought to a helper class, but only fleetingly thinking that was the incorrect way of doing it in an object oriented paradigm.

      Although I'm still not sure even adding a menu item with a helper class is possible.
      Normally to set up a menu item the code looks like this:

          utilMenu = menuBar()->addMenu("Utilities");
      
          // utilites menu list
          QAction *networkAction = new QAction("Network",this);
      
          networkAction->setCheckable(false);
      
          utilMenu->addAction(networkAction);
          utilMenu->addSeparator();
      
          connect(networkAction, &QAction::triggered, this, &ServiceAppLayout::onNetworkAction);
      

      and I tried, I can't access utilMenu->addAction from main.cpp even though I made utilMenu
      public.

      w.utilMenu.
      

      Nothing would come up after the "." like normal so I realized something isn't quite right and I can't access those members.

      I take it actually inheriting a class with a custom ui is impossible?

      mrjjM Offline
      mrjjM Offline
      mrjj
      Lifetime Qt Champion
      wrote on last edited by mrjj
      #7

      @graniteDev
      Well it is inherited already as UI file is just an XML file - Creator uses to create the setupUI() function that contains plain c++ code to create the form layout. 100% like manually code.
      the UI file is not used runtime in anyway.

      I think this is why im not 100% sure what goes wrong or what you try. :)

      1 Reply Last reply
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      • mrjjM mrjj

        Oh, wait. You seen a lot of this in connect statements and hence "this" seems important ?
        Normally inside say Mainwindow, often one part of the connect statement is this as slot lives in mainwindow.
        But it dont have to be "this" . its just because, its inside the class in question.

        Its perfectly legal not to have "this"
        connect( ui->someWidget, SIGNAl, ui->OTHER, SLOT( this slot lives in OTHER ))

        G Offline
        G Offline
        graniteDev
        wrote on last edited by
        #8

        @mrjj Yes, I understand what "this" is doing. The slot part of the connection just needs to know what object to find the slot in.

        1 Reply Last reply
        1
        • mrjjM Offline
          mrjjM Offline
          mrjj
          Lifetime Qt Champion
          wrote on last edited by
          #9

          Ok, good.
          Just checking. :)

          But would utilMenu not live inside the UI ?
          so its
          w.UI->utilMenu ?
          (UI is most likely still private if you didnt move it )

          G 1 Reply Last reply
          1
          • mrjjM mrjj

            Ok, good.
            Just checking. :)

            But would utilMenu not live inside the UI ?
            so its
            w.UI->utilMenu ?
            (UI is most likely still private if you didnt move it )

            G Offline
            G Offline
            graniteDev
            wrote on last edited by
            #10

            @mrjj OH that's a good point - I could have done it that way, but I just made a helper function that allows me to add an action to the menu. I believe now I can connect to it with a helper class....I'll try it and see what happens

            mrjjM 1 Reply Last reply
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            • G graniteDev

              @mrjj OH that's a good point - I could have done it that way, but I just made a helper function that allows me to add an action to the menu. I believe now I can connect to it with a helper class....I'll try it and see what happens

              mrjjM Offline
              mrjjM Offline
              mrjj
              Lifetime Qt Champion
              wrote on last edited by mrjj
              #11

              @graniteDev
              Hi
              Adding a public helper function to allow connects
              is better design than make UI public.

              Also as a note.

              Its also ok to make connect from signal to signal to surface inner widgets signals to the outside.
              So you declare new public signals and internally hook widget signal to new public signal.

              Then you can connect from outside to the public signal interface and in that way totally hide
              what the widgets really are inside. Only signals are visible.
              If you later change a a widget to other type, you just need to fix the internal mapping.
              Any external connections still just see the public signal interface and no change is needed.

              So for example a custom fileDialog have the signal FileSelected that outside can use.
              What widget internally that actually got the input is not important from outside.
              They just use FileSelected and knows nothing about its inner design.
              On larger programs, such details hiding are worth the extra code in gold.

              G 1 Reply Last reply
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              • mrjjM mrjj

                @graniteDev
                Hi
                Adding a public helper function to allow connects
                is better design than make UI public.

                Also as a note.

                Its also ok to make connect from signal to signal to surface inner widgets signals to the outside.
                So you declare new public signals and internally hook widget signal to new public signal.

                Then you can connect from outside to the public signal interface and in that way totally hide
                what the widgets really are inside. Only signals are visible.
                If you later change a a widget to other type, you just need to fix the internal mapping.
                Any external connections still just see the public signal interface and no change is needed.

                So for example a custom fileDialog have the signal FileSelected that outside can use.
                What widget internally that actually got the input is not important from outside.
                They just use FileSelected and knows nothing about its inner design.
                On larger programs, such details hiding are worth the extra code in gold.

                G Offline
                G Offline
                graniteDev
                wrote on last edited by
                #12

                @mrjj Ok, thank you for the advice. I have it working.

                helper.cpp

                #include "helper.h"
                #include "exwidget.h"
                
                helper::helper(QWidget *parent) : QWidget(parent)
                {
                
                }
                
                void helper::callWidget()
                {
                    ExWidget *exWidget = new ExWidget(this);
                    exWidget->setWindowFlags(Qt::Window);
                    exWidget->setAttribute(Qt::WA_DeleteOnClose);
                    exWidget->setWindowTitle("Vmap Viewer");
                    exWidget->show();
                }
                

                main.cpp

                #include <serviceAppLayout.h>
                #include <QApplication>
                #include <QMenu>
                #include <QAction>
                #include "widgettest1.h"
                #include "widgettest2.h"
                #include "helper.h"
                
                int main(int argc, char *argv[])
                {
                    QApplication a(argc, argv);
                
                
                    ServiceAppLayout w;
                    helper *h = new helper(&w);
                
                    widgettest1 *widgetTest1_A = new widgettest1(&w);
                    widgettest2 *widgetTest2_B = new widgettest2(&w);
                
                    w.addCustomWidget(widgetTest1_A, "Test Widget 1");
                    w.addCustomWidget(widgetTest2_B, "Test Widget 2");
                
                    w.initializeLayout();
                
                    QAction * testAction = new QAction("Test Menu Item", &w);
                    w.addMenuItem(w.devMenu, testAction);
                    QObject::connect(testAction, &QAction::triggered, h, &helper::callWidget);
                
                    w.show();
                
                    return a.exec();
                }
                

                Running it loads the layout, the widgets, and the new menu item, and clicking the menu item launches the widget as desired.

                Thank you again for your help!

                1 Reply Last reply
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                • mrjjM Offline
                  mrjjM Offline
                  mrjj
                  Lifetime Qt Champion
                  wrote on last edited by
                  #13

                  Hi
                  Np :)
                  Super. And you use the new connection syntax :) \o/ +1
                  Just as a note
                  QObject::connect(testAction, &QAction::triggered, h, &helper::callWidget);

                  Could have been made with a lambda to avoid the helper but helper is also fine.

                  G 1 Reply Last reply
                  1
                  • mrjjM mrjj

                    Hi
                    Np :)
                    Super. And you use the new connection syntax :) \o/ +1
                    Just as a note
                    QObject::connect(testAction, &QAction::triggered, h, &helper::callWidget);

                    Could have been made with a lambda to avoid the helper but helper is also fine.

                    G Offline
                    G Offline
                    graniteDev
                    wrote on last edited by
                    #14

                    @mrjj It's true, but I'm trying to avoid piling tons of code into main, and just keep it as much as I can to one line commands. In the actual implementation there will need to be quite a lot more code in the helper file.

                    mrjjM 1 Reply Last reply
                    1
                    • G graniteDev

                      @mrjj It's true, but I'm trying to avoid piling tons of code into main, and just keep it as much as I can to one line commands. In the actual implementation there will need to be quite a lot more code in the helper file.

                      mrjjM Offline
                      mrjjM Offline
                      mrjj
                      Lifetime Qt Champion
                      wrote on last edited by
                      #15

                      @graniteDev
                      That is a good plan.
                      Also a helper class is more OOP than multiple lambdas in main :)

                      1 Reply Last reply
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