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creating cpp library using qt

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  • jsulmJ jsulm

    @amruz Add

    QT       += widgets
    
    

    Fix the LIBS line (no space between -L and the path):

    LIBS += -L/home/amruz/build-worksharedlib-Desktop_Qt_5_7_0_GCC_64bit-Debug -lworksharedlib
    
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    amruz
    wrote on last edited by
    #11

    @jsulm said in creating cpp library using qt:

    QT += widgets

    can you also help me in writing the main.cpp file..
    how to actually call the mainwindow there with the library output in it

    jsulmJ 1 Reply Last reply
    0
    • A amruz

      @jsulm said in creating cpp library using qt:

      QT += widgets

      can you also help me in writing the main.cpp file..
      how to actually call the mainwindow there with the library output in it

      jsulmJ Online
      jsulmJ Online
      jsulm
      Lifetime Qt Champion
      wrote on last edited by
      #12

      @amruz You use it as any other library. You're already doing it with Qt.
      Just include the header file of your library and use it. For example create an instance of Worksharedlib.

      #include "sharedlib.h"
      
      int main()
      {
          ...
          Worksharedlib lib;
          lib.show();
          ...
      }

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

      A 1 Reply Last reply
      0
      • jsulmJ jsulm

        @amruz You use it as any other library. You're already doing it with Qt.
        Just include the header file of your library and use it. For example create an instance of Worksharedlib.

        #include "sharedlib.h"
        
        int main()
        {
            ...
            Worksharedlib lib;
            lib.show();
            ...
        }
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        amruz
        wrote on last edited by
        #13

        @jsulm said in creating cpp library using qt:

        Worksharedlib lib;
        lib.show();

        i used the same way only.. but i am getting error as follows

        /home/amruz/worksharedlib/worksharedlib.h:14: error: undefined reference to `vtable for Worksharedlib'

        jsulmJ 1 Reply Last reply
        0
        • A amruz

          @jsulm said in creating cpp library using qt:

          Worksharedlib lib;
          lib.show();

          i used the same way only.. but i am getting error as follows

          /home/amruz/worksharedlib/worksharedlib.h:14: error: undefined reference to `vtable for Worksharedlib'

          jsulmJ Online
          jsulmJ Online
          jsulm
          Lifetime Qt Champion
          wrote on last edited by
          #14

          @amruz Will probably not solve that error, but this looks wrong as well:

          QT -= gui
          

          Your app is going to show an UI, right? Then it is a gui app:

          QT += core gui widgets
          

          Don't forget to rerun qmake after changing pro file and rebuild.

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

          A 1 Reply Last reply
          1
          • jsulmJ jsulm

            @amruz Will probably not solve that error, but this looks wrong as well:

            QT -= gui
            

            Your app is going to show an UI, right? Then it is a gui app:

            QT += core gui widgets
            

            Don't forget to rerun qmake after changing pro file and rebuild.

            A Offline
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            amruz
            wrote on last edited by
            #15

            @jsulm said in creating cpp library using qt:

            QT += core gui widgets

            this is a console application actually..is that the problem?

            jsulmJ 1 Reply Last reply
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            • A amruz

              @jsulm said in creating cpp library using qt:

              QT += core gui widgets

              this is a console application actually..is that the problem?

              jsulmJ Online
              jsulmJ Online
              jsulm
              Lifetime Qt Champion
              wrote on last edited by
              #16

              @amruz If it is a console application then why do you want to use a library which provides an UI class:

              class WORKSHAREDLIBSHARED_EXPORT Worksharedlib:public QWidget
              {
              
                 Q_OBJECT
              public:
                  //Worksharedlib();
                  Worksharedlib(QWidget *parent = 0);
                  ~Worksharedlib() {}
              
              private slots:
                 void handleButton();
                 void m_buttonClicked();
              
              private:
                 QPushButton *m_button;
                 QLineEdit *m_textbox;
                 QHBoxLayout *layout;
                 QWidget *window;
                 QLabel * label;
                 QWidget *frame;
              };
              

              ?

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

              A 1 Reply Last reply
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              • jsulmJ jsulm

                @amruz If it is a console application then why do you want to use a library which provides an UI class:

                class WORKSHAREDLIBSHARED_EXPORT Worksharedlib:public QWidget
                {
                
                   Q_OBJECT
                public:
                    //Worksharedlib();
                    Worksharedlib(QWidget *parent = 0);
                    ~Worksharedlib() {}
                
                private slots:
                   void handleButton();
                   void m_buttonClicked();
                
                private:
                   QPushButton *m_button;
                   QLineEdit *m_textbox;
                   QHBoxLayout *layout;
                   QWidget *window;
                   QLabel * label;
                   QWidget *frame;
                };
                

                ?

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                amruz
                wrote on last edited by
                #17

                @jsulm which application should i use to test this library?

                jsulmJ 1 Reply Last reply
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                • A amruz

                  @jsulm which application should i use to test this library?

                  jsulmJ Online
                  jsulmJ Online
                  jsulm
                  Lifetime Qt Champion
                  wrote on last edited by
                  #18

                  @amruz gui?

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

                  A 1 Reply Last reply
                  0
                  • jsulmJ jsulm

                    @amruz gui?

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                    amruz
                    wrote on last edited by
                    #19

                    @jsulm do you mean qt widget application?

                    jsulmJ 1 Reply Last reply
                    0
                    • A amruz

                      @jsulm do you mean qt widget application?

                      jsulmJ Online
                      jsulmJ Online
                      jsulm
                      Lifetime Qt Champion
                      wrote on last edited by
                      #20

                      @amruz Yes. You're using widgets - so it must be a gui application with widgets, right?

                      QT += core gui widgets
                      

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

                      A 2 Replies Last reply
                      0
                      • jsulmJ jsulm

                        @amruz Yes. You're using widgets - so it must be a gui application with widgets, right?

                        QT += core gui widgets
                        
                        A Offline
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                        amruz
                        wrote on last edited by
                        #21

                        @jsulm when i try to include this library in a widget application also i am getting the same error..

                        this is the .pro file of my widgetapplication

                        #-------------------------------------------------
                        #
                        # Project created by QtCreator 2017-07-27T17:19:21
                        #
                        #-------------------------------------------------
                        
                        QT       += core gui widgets
                        
                        greaterThan(QT_MAJOR_VERSION, 4): QT += widgets
                        
                        TARGET = sharedlibtryinwidget
                        TEMPLATE = app
                        
                        
                        SOURCES += main.cpp\
                                mainwindow.cpp
                        
                        HEADERS  += mainwindow.h
                        
                        DEPENDPATH += /home/amruz/worksharedlib
                        INCLUDEPATH += /home/amruz/worksharedlib
                        LIBS += -L/home/amruz/build-worksharedlib-Desktop_Qt_5_7_0_GCC_64bit-Debug -lworksharedlib
                        
                        
                        
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                        • A amruz

                          @jsulm when i try to include this library in a widget application also i am getting the same error..

                          this is the .pro file of my widgetapplication

                          #-------------------------------------------------
                          #
                          # Project created by QtCreator 2017-07-27T17:19:21
                          #
                          #-------------------------------------------------
                          
                          QT       += core gui widgets
                          
                          greaterThan(QT_MAJOR_VERSION, 4): QT += widgets
                          
                          TARGET = sharedlibtryinwidget
                          TEMPLATE = app
                          
                          
                          SOURCES += main.cpp\
                                  mainwindow.cpp
                          
                          HEADERS  += mainwindow.h
                          
                          DEPENDPATH += /home/amruz/worksharedlib
                          INCLUDEPATH += /home/amruz/worksharedlib
                          LIBS += -L/home/amruz/build-worksharedlib-Desktop_Qt_5_7_0_GCC_64bit-Debug -lworksharedlib
                          
                          
                          
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                          amruz
                          wrote on last edited by
                          #22

                          @amruz i also found that when destructor is not included this type of error may occur..but when i added destructor also the same problem exists

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                          • jsulmJ jsulm

                            @amruz Yes. You're using widgets - so it must be a gui application with widgets, right?

                            QT += core gui widgets
                            
                            A Offline
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                            amruz
                            wrote on last edited by amruz
                            #23

                            @jsulm it worked finally! thanks a lot for all the help

                            the problem was qobject in the library , i removed it and it worked.

                            1 Reply Last reply
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