Include Library into Library. Load Library at runntime. ( some Library Magic :) )

[M001]

Hey guys, i need some help at working with librarys.

this is my structure:

• MyClass (subclass of QWidget)
  this class sould implement some functions, which should be used by the subclasses.
  this class is packed into a library

• MySubClass (subclass of MyClass)

• MySubClass1 (subclass of MyClass)

• ... many more subclasses of MyClass
  all these classes where packed into different librarys
  theses classes have different UIs wich sould be loaded into a different programm

now i want to load the different MySubClassX librarys at runntime and show their UIs. I hope you get what i want to do? Here is my code:

MyClass.pro

@QT += widgets

TARGET = MyClass
TEMPLATE = lib

DEFINES += MYCLASS_LIBRARY

SOURCES += myclass.cpp

HEADERS += myclass.h
myclass_global.h

unix:!symbian {
maemo5 {
target.path = /opt/usr/lib
} else {
target.path = /usr/lib
}
INSTALLS += target
}@

MyClass.h

@#ifndef MYCLASS_H
#define MYCLASS_H

#include <QtCore>
#include <QWidget>
#include "myclass_global.h"

class MYCLASSSHARED_EXPORT MyClass : public QWidget
{
Q_OBJECT

public:
MyClass(QWidget *parent = 0);

protected:
QString someString;

public slots:
int doSomething( int a, int b );

};

#endif // MYCLASS_H
@

MyClass_global.h

@#ifndef MYCLASS_GLOBAL_H
#define MYCLASS_GLOBAL_H

#include <QtCore/qglobal.h>

#if defined(MYCLASS_LIBRARY)

define MYCLASSSHARED_EXPORT Q_DECL_EXPORT

#else

define MYCLASSSHARED_EXPORT Q_DECL_IMPORT

#endif

#endif // MYCLASS_GLOBAL_H
@

MyClass.cpp

@#include "myclass.h"

MyClass::MyClass(QWidget *parent) :
QWidget(parent)
{
}

int MyClass::doSomething(int a, int b)
{
return a+b;
}
@

MySubClass.pro

@QT += widgets

TARGET = MySubClass
TEMPLATE = lib

INCLUDEPATH += "C:/Testing/" #here are the .h -Files of MyClass
LIBS += "C:/Testing/MyClass.dll"

DEFINES += MYSUBCLASS_LIBRARY

SOURCES += mysubclass.cpp

HEADERS += mysubclass.h
mysubclass_global.h

unix:!symbian {
maemo5 {
target.path = /opt/usr/lib
} else {
target.path = /usr/lib
}
INSTALLS += target
}

FORMS +=
mysubclass.ui@

MySubClass.h

@#ifndef MYSUBCLASS_H
#define MYSUBCLASS_H

#include <QtCore>
#include <QMainWindow>
#include "mysubclass_global.h"
#include "myclass.h"

namespace Ui {
class MySubClass;
}

class MYSUBCLASSSHARED_EXPORT MySubClass : public MyClass
{
Q_OBJECT

public:
MySubClass(MyClass *parent = 0);
~MySubClass();

private:
Ui::MySubClass *ui;

};

extern "C" MYSUBCLASSSHARED_EXPORT MySubClass* create();

#endif // MYSUBCLASS_H
@

MySubClass_global.h

@#ifndef MYSUBCLASS_GLOBAL_H
#define MYSUBCLASS_GLOBAL_H

#include <QtCore/qglobal.h>

#if defined(MYSUBCLASS_LIBRARY)

define MYSUBCLASSSHARED_EXPORT Q_DECL_EXPORT

#else

define MYSUBCLASSSHARED_EXPORT Q_DECL_IMPORT

#endif

#endif // MYSUBCLASS_GLOBAL_H
@

MySubClass.cpp

@#include "mysubclass.h"
#include "ui_mysubclass.h"

MySubClass::MySubClass(MyClass *parent) :
MyClass( parent ),
ui( new Ui::MySubClass )
{
ui->setupUi(this);
}

MySubClass::~MySubClass()
{
delete ui;
}

extern "C" MySubClass* create()
{
MySubClass newinstance;
return &newinstance;
}

@

LoadLibrary.pro

@QT += core gui

greaterThan(QT_MAJOR_VERSION, 4): QT += widgets

TARGET = LoadLibary
TEMPLATE = app

INCLUDEPATH += "C:/Testing/"

SOURCES += main.cpp
mainwindow.cpp

HEADERS += mainwindow.h

FORMS += mainwindow.ui
@

LoadLibrary.h

@#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>
#include <QLibrary>
#include "myclass.h"

namespace Ui {
class MainWindow;
}

class MainWindow : public QMainWindow
{
Q_OBJECT

public:
explicit MainWindow(QWidget *parent = 0);
~MainWindow();

private slots:
void on_pushButton_clicked();

private:
Ui::MainWindow ui;
//MyClass instance;
};

#endif // MAINWINDOW_H
@

LoadLibrary.cpp

@
#include "mainwindow.h"
#include "ui_mainwindow.h"

MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)
{
ui->setupUi(this);
}

MainWindow::~MainWindow()
{
delete ui;
}

void MainWindow::on_pushButton_clicked()
{
typedef MyClass (*MySubClass)();
QLibrary myLib("MySubClass");
MySubClass create = (MySubClass) myLib.resolve("create");
if(create){
MyClass a = create();
a->show();
}
}

@

main.cpp

@#include "mainwindow.h"
#include <QApplication>

int main(int argc, char *argv[])
{
QApplication a(argc, argv);
MainWindow w;
w.show();

return a.exec();

}
@

so until now it dosn't work. in LoadLibrary.cpp is an error. I can't get an instance of my MySubClass class.
what am i doing wrong? All the .h-files and .dll are in the directory "C:/Testing/".

[SGaist]

Hi,

Did you check that the library is loaded ? What errorString returns ?

[dbzhang800]

@
extern "C" MySubClass* create()
{
MySubClass newinstance;
return &newinstance;
}
@

Hi,

You return a wild pointer here.