creating cpp library using qt

[amruz]

@jsulm the pro file of my application which calls the library is

QT += core
QT -= gui

CONFIG += c++11

TARGET = testcretedlibrary
CONFIG += console
CONFIG -= app_bundle

TEMPLATE = app

SOURCES += main.cpp

DEPENDPATH += /home/amruz/worksharedlib
INCLUDEPATH += /home/amruz/worksharedlib
LIBS += -L /home/amruz/build-worksharedlib-Desktop_Qt_5_7_0_GCC_64bit-Debug -lworksharedlib

[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

[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

[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();
    ...
}

[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'

[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.

[amruz]

@jsulm said in creating cpp library using qt:

QT += core gui widgets

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

[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;
};

?

[amruz]

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

[jsulm]

@amruz gui?

[amruz]

@jsulm do you mean qt widget application?

[jsulm]

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

QT += core gui widgets

[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

[amruz]

@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

[amruz]

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

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