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Connect signals and slots of a class from another class

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  • T Offline
    T Offline
    thewiggin
    wrote on last edited by
    #7

    Here's the example with the relative information included. the EnglishPage only has one layout and if the connect line is commented out the code compiles and does add the button to each page in the stack.

    gui.h.......

    #include <QDialog>
     
    QT_BEGIN_NAMESPACE
     
    QT_END_NAMESPACE
     
    class gui : public QDialog
    {
        Q_OBJECT
     
    public:
        gui(QWidget *parent = nullptr);
        ~gui();
     
    };
    

    gui.c........

    #include "gui.h"
    #include <QtWidgets>
    #include "mylistwidget.h"
     
    gui::gui(QWidget *parent)
        : QDialog(parent)
    {
        setFixedSize(800,600);
        setWindowTitle(tr("Gui Tests"));
     
        QVBoxLayout *mainLayout = new QVBoxLayout;
        QTabWidget *tabWidget = new QTabWidget;
        MyListWidget *myListWidget = new MyListWidget;
        QScrollArea *myListWidgetScrollArea = new QScrollArea;
        myListWidgetScrollArea->setWidget(myListWidget);
        tabWidget->addTab(myListWidgetScrollArea, "List Widget");
        mainLayout->addWidget(tabWidget);
     
        for(int i = 0; i < myListWidget->pageStack->count(); ++i)
        {
            QVBoxLayout *pageLay = myListWidget->pageStack->widget(i)->findChild<QVBoxLayout*>();
            if(pageLay)
            {
                QPushButton *applyBtn = new QPushButton("push");
                pageLay->addWidget(applyBtn, 0, Qt::AlignCenter);
                connect(applyBtn, &QPushButton::clicked, myListWidget->pageStack->widget(i), &EnglishPage::btnClicked);
            }
        }
    

    Mylistwidget.h…..

    #include <QListWidget>
    #include <QStackedWidget>

    class MyListWidget : public QWidget
    {
    Q_OBJECT

    public:
    MyListWidget();
    QStackedWidget *pageStack;
    QListWidget *listWidget;
    }

    setLayout(mainLayout);
    setWindowTitle(QGuiApplication::applicationDisplayName());
    }

    class EnglishPage : public QWidget
    {
    Q_OBJECT
    public:
    EnglishPage(QWidget *parent = 0);

    public slots:
    void btnClicked(void);
    };

    @CP71 I widget does return const. I'm not too familiar with C++. The hover bubble over the function reads QWidget *QStackedWidget::(int index) const. I guess const on the end makes the return const? How do I "remove" the const?

    Pl45m4P CP71C 3 Replies Last reply
    0
    • T thewiggin

      Here's the example with the relative information included. the EnglishPage only has one layout and if the connect line is commented out the code compiles and does add the button to each page in the stack.

      gui.h.......

      #include <QDialog>
       
      QT_BEGIN_NAMESPACE
       
      QT_END_NAMESPACE
       
      class gui : public QDialog
      {
          Q_OBJECT
       
      public:
          gui(QWidget *parent = nullptr);
          ~gui();
       
      };
      

      gui.c........

      #include "gui.h"
      #include <QtWidgets>
      #include "mylistwidget.h"
       
      gui::gui(QWidget *parent)
          : QDialog(parent)
      {
          setFixedSize(800,600);
          setWindowTitle(tr("Gui Tests"));
       
          QVBoxLayout *mainLayout = new QVBoxLayout;
          QTabWidget *tabWidget = new QTabWidget;
          MyListWidget *myListWidget = new MyListWidget;
          QScrollArea *myListWidgetScrollArea = new QScrollArea;
          myListWidgetScrollArea->setWidget(myListWidget);
          tabWidget->addTab(myListWidgetScrollArea, "List Widget");
          mainLayout->addWidget(tabWidget);
       
          for(int i = 0; i < myListWidget->pageStack->count(); ++i)
          {
              QVBoxLayout *pageLay = myListWidget->pageStack->widget(i)->findChild<QVBoxLayout*>();
              if(pageLay)
              {
                  QPushButton *applyBtn = new QPushButton("push");
                  pageLay->addWidget(applyBtn, 0, Qt::AlignCenter);
                  connect(applyBtn, &QPushButton::clicked, myListWidget->pageStack->widget(i), &EnglishPage::btnClicked);
              }
          }
      

      Mylistwidget.h…..

      #include <QListWidget>
      #include <QStackedWidget>

      class MyListWidget : public QWidget
      {
      Q_OBJECT

      public:
      MyListWidget();
      QStackedWidget *pageStack;
      QListWidget *listWidget;
      }

      setLayout(mainLayout);
      setWindowTitle(QGuiApplication::applicationDisplayName());
      }

      class EnglishPage : public QWidget
      {
      Q_OBJECT
      public:
      EnglishPage(QWidget *parent = 0);

      public slots:
      void btnClicked(void);
      };

      @CP71 I widget does return const. I'm not too familiar with C++. The hover bubble over the function reads QWidget *QStackedWidget::(int index) const. I guess const on the end makes the return const? How do I "remove" the const?

      Pl45m4P Offline
      Pl45m4P Offline
      Pl45m4
      wrote on last edited by Pl45m4
      #8

      @thewiggin said in Connect signals and slots of a class from another class:

      void btnClicked(void);

      What happens if you remove the void parameter, since clicked signal passes a boolean by default to the slot?
      (Just leave it empty)


      If debugging is the process of removing software bugs, then programming must be the process of putting them in.

      ~E. W. Dijkstra

      CP71C 1 Reply Last reply
      2
      • T thewiggin

        Here's the example with the relative information included. the EnglishPage only has one layout and if the connect line is commented out the code compiles and does add the button to each page in the stack.

        gui.h.......

        #include <QDialog>
         
        QT_BEGIN_NAMESPACE
         
        QT_END_NAMESPACE
         
        class gui : public QDialog
        {
            Q_OBJECT
         
        public:
            gui(QWidget *parent = nullptr);
            ~gui();
         
        };
        

        gui.c........

        #include "gui.h"
        #include <QtWidgets>
        #include "mylistwidget.h"
         
        gui::gui(QWidget *parent)
            : QDialog(parent)
        {
            setFixedSize(800,600);
            setWindowTitle(tr("Gui Tests"));
         
            QVBoxLayout *mainLayout = new QVBoxLayout;
            QTabWidget *tabWidget = new QTabWidget;
            MyListWidget *myListWidget = new MyListWidget;
            QScrollArea *myListWidgetScrollArea = new QScrollArea;
            myListWidgetScrollArea->setWidget(myListWidget);
            tabWidget->addTab(myListWidgetScrollArea, "List Widget");
            mainLayout->addWidget(tabWidget);
         
            for(int i = 0; i < myListWidget->pageStack->count(); ++i)
            {
                QVBoxLayout *pageLay = myListWidget->pageStack->widget(i)->findChild<QVBoxLayout*>();
                if(pageLay)
                {
                    QPushButton *applyBtn = new QPushButton("push");
                    pageLay->addWidget(applyBtn, 0, Qt::AlignCenter);
                    connect(applyBtn, &QPushButton::clicked, myListWidget->pageStack->widget(i), &EnglishPage::btnClicked);
                }
            }
        

        Mylistwidget.h…..

        #include <QListWidget>
        #include <QStackedWidget>

        class MyListWidget : public QWidget
        {
        Q_OBJECT

        public:
        MyListWidget();
        QStackedWidget *pageStack;
        QListWidget *listWidget;
        }

        setLayout(mainLayout);
        setWindowTitle(QGuiApplication::applicationDisplayName());
        }

        class EnglishPage : public QWidget
        {
        Q_OBJECT
        public:
        EnglishPage(QWidget *parent = 0);

        public slots:
        void btnClicked(void);
        };

        @CP71 I widget does return const. I'm not too familiar with C++. The hover bubble over the function reads QWidget *QStackedWidget::(int index) const. I guess const on the end makes the return const? How do I "remove" the const?

        CP71C Offline
        CP71C Offline
        CP71
        wrote on last edited by CP71
        #9

        @thewiggin
        const at the end: "QWidget *QStackedWidget::(int index) const" means function body of class can not change its member varables ( variables are defined in .h )

        1 Reply Last reply
        1
        • T thewiggin

          Here's the example with the relative information included. the EnglishPage only has one layout and if the connect line is commented out the code compiles and does add the button to each page in the stack.

          gui.h.......

          #include <QDialog>
           
          QT_BEGIN_NAMESPACE
           
          QT_END_NAMESPACE
           
          class gui : public QDialog
          {
              Q_OBJECT
           
          public:
              gui(QWidget *parent = nullptr);
              ~gui();
           
          };
          

          gui.c........

          #include "gui.h"
          #include <QtWidgets>
          #include "mylistwidget.h"
           
          gui::gui(QWidget *parent)
              : QDialog(parent)
          {
              setFixedSize(800,600);
              setWindowTitle(tr("Gui Tests"));
           
              QVBoxLayout *mainLayout = new QVBoxLayout;
              QTabWidget *tabWidget = new QTabWidget;
              MyListWidget *myListWidget = new MyListWidget;
              QScrollArea *myListWidgetScrollArea = new QScrollArea;
              myListWidgetScrollArea->setWidget(myListWidget);
              tabWidget->addTab(myListWidgetScrollArea, "List Widget");
              mainLayout->addWidget(tabWidget);
           
              for(int i = 0; i < myListWidget->pageStack->count(); ++i)
              {
                  QVBoxLayout *pageLay = myListWidget->pageStack->widget(i)->findChild<QVBoxLayout*>();
                  if(pageLay)
                  {
                      QPushButton *applyBtn = new QPushButton("push");
                      pageLay->addWidget(applyBtn, 0, Qt::AlignCenter);
                      connect(applyBtn, &QPushButton::clicked, myListWidget->pageStack->widget(i), &EnglishPage::btnClicked);
                  }
              }
          

          Mylistwidget.h…..

          #include <QListWidget>
          #include <QStackedWidget>

          class MyListWidget : public QWidget
          {
          Q_OBJECT

          public:
          MyListWidget();
          QStackedWidget *pageStack;
          QListWidget *listWidget;
          }

          setLayout(mainLayout);
          setWindowTitle(QGuiApplication::applicationDisplayName());
          }

          class EnglishPage : public QWidget
          {
          Q_OBJECT
          public:
          EnglishPage(QWidget *parent = 0);

          public slots:
          void btnClicked(void);
          };

          @CP71 I widget does return const. I'm not too familiar with C++. The hover bubble over the function reads QWidget *QStackedWidget::(int index) const. I guess const on the end makes the return const? How do I "remove" the const?

          CP71C Offline
          CP71C Offline
          CP71
          wrote on last edited by
          #10

          @thewiggin
          I don't see anything strange! or it seems so.
          I know, what I say now could be strange, but try to remove the build folder via file explorer.
          I don't know why, sometimes when I see something that is strange and it seems inexplicable this operation removes the issue.
          I don't say this is the case, but you don't have anything to lose ;)

          1 Reply Last reply
          1
          • Pl45m4P Pl45m4

            @thewiggin said in Connect signals and slots of a class from another class:

            void btnClicked(void);

            What happens if you remove the void parameter, since clicked signal passes a boolean by default to the slot?
            (Just leave it empty)

            CP71C Offline
            CP71C Offline
            CP71
            wrote on last edited by
            #11

            @Pl45m4
            I have tried to do this.
            I have made connect with and without void but I haven't seen the issue

            1 Reply Last reply
            1
            • T Offline
              T Offline
              thewiggin
              wrote on last edited by
              #12

              @CP71 no luck when removing build folder and retrying

              @Pl45m4 changing the slot from void to nothing did not resolve this

              1 Reply Last reply
              0
              • T Offline
                T Offline
                thewiggin
                wrote on last edited by
                #13

                Here's my workaround, it seems needlessly complex and has me begging the question of if its possible to connect to the slot of another class outside that class. All the declarations I can find use "this" as the third augment.

                gui.c I added this at the bottom of the for loop, right after adding the button the the layout.

                EnglishPage *pg = dynamic_cast<EnglishPage*>(myListWidget->pageStack->widget(i));
                            if(pg)
                            {
                                 pg->setBtn(applyBtn);
                            }
                            else
                            {
                                qDebug() << "failed to connect apply btn for english page";
                           }
                

                I changed the public slot in EnglishPage to a private slot and added a public function called setBtn.

                void EnglishPage::setBtn(QPushButton *btn)
                {
                    connect(btn, &QPushButton::clicked, this, &EnglishPage::btnClicked);
                }
                
                CP71C 1 Reply Last reply
                1
                • T Offline
                  T Offline
                  thewiggin
                  wrote on last edited by
                  #14

                  Well shockingly it was needlessly complex.

                  The below line works in context with the other code posted. I will aggregate it together in this post eventually for a clean solution unless someone provides a better one. I had to change the slot back to public from private.

                  connect(applyBtn, &QPushButton::clicked, dynamic_cast<EnglishPage*>(myListWidget->pageStack->widget(i)), &EnglishPage::btnclicked);
                  
                  CP71C 1 Reply Last reply
                  1
                  • T thewiggin

                    Well shockingly it was needlessly complex.

                    The below line works in context with the other code posted. I will aggregate it together in this post eventually for a clean solution unless someone provides a better one. I had to change the slot back to public from private.

                    connect(applyBtn, &QPushButton::clicked, dynamic_cast<EnglishPage*>(myListWidget->pageStack->widget(i)), &EnglishPage::btnclicked);
                    
                    CP71C Offline
                    CP71C Offline
                    CP71
                    wrote on last edited by CP71
                    #15

                    @thewiggin
                    Sorry, my mistake :(
                    There is something strange!
                    myListWidget-> pageStack-> widget (i) returns QWidget * and not EnglishPage *, for this it didn't found btnClicked.
                    Sometimes the solution is under our eyes but it hides under them:;

                    1 Reply Last reply
                    2
                    • T thewiggin

                      Here's my workaround, it seems needlessly complex and has me begging the question of if its possible to connect to the slot of another class outside that class. All the declarations I can find use "this" as the third augment.

                      gui.c I added this at the bottom of the for loop, right after adding the button the the layout.

                      EnglishPage *pg = dynamic_cast<EnglishPage*>(myListWidget->pageStack->widget(i));
                                  if(pg)
                                  {
                                       pg->setBtn(applyBtn);
                                  }
                                  else
                                  {
                                      qDebug() << "failed to connect apply btn for english page";
                                 }
                      

                      I changed the public slot in EnglishPage to a private slot and added a public function called setBtn.

                      void EnglishPage::setBtn(QPushButton *btn)
                      {
                          connect(btn, &QPushButton::clicked, this, &EnglishPage::btnClicked);
                      }
                      
                      CP71C Offline
                      CP71C Offline
                      CP71
                      wrote on last edited by CP71
                      #16

                      @thewiggin said in Connect signals and slots of a class from another class:

                      Here's my workaround, it seems needlessly complex and has me begging the question of if its possible to connect to the slot of another class outside that class. All the declarations I can find use "this" as the third augment.

                      Yes of course!
                      you see "this" because normally the sender or/and the receiver is the class itself, but you can connect one or two classes that arent the classe itself!
                      But this you already see in your last post!

                      1 Reply Last reply
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