Skip to content
  • Categories
  • Recent
  • Tags
  • Popular
  • Users
  • Groups
  • Search
  • Get Qt
  • Unsolved
Collapse
qtws26_logo

The Qt Event of the Year: Qt World Summit 2026

Save Your Spot >
Brand Logo
  1. Home
  2. Qt Development
  3. General and Desktop
  4. creating cpp library using qt
Qt 6.12 LTS is out! See what's new in the release blog

creating cpp library using qt

Scheduled Pinned Locked Moved General and Desktop
23 Posts 3 Posters 21.6k Views 2 Watching
  • Oldest to Newest
  • Newest to Oldest
  • Most Votes
Reply
  • Reply as topic
Log in to reply
This topic has been deleted. Only users with topic management privileges can see it.
  • 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 Offline
    jsulmJ Offline
    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
      A Offline
      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
      0
      • 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 Offline
        jsulmJ Offline
        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
        0
        • 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;
          };
          

          ?

          A Offline
          A Offline
          amruz
          wrote on last edited by
          #17

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

          jsulmJ 1 Reply Last reply
          0
          • A amruz

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

            jsulmJ Offline
            jsulmJ Offline
            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?

              A Offline
              A Offline
              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 Offline
                jsulmJ Offline
                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
                  A Offline
                  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
                  
                  
                  
                  A 1 Reply Last reply
                  0
                  • 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
                    
                    
                    
                    A Offline
                    A Offline
                    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

                    1 Reply 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
                      A Offline
                      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
                      0

                      • Login

                      • Login or register to search.
                      • First post
                        Last post
                      0
                      • Categories
                      • Recent
                      • Tags
                      • Popular
                      • Users
                      • Groups
                      • Search
                      • Get Qt
                      • Unsolved