Program crashes because of wrong usage of slots and signals - c++

Question

What I'm trying to do is to call an time consuming operation (MockClamWrapper::loadDatabase()) in a separate thread at the moment of creation of my window and then to update my window once the operation is completed. Here is the code that I have.
MockClamWrapper.h
class MockClamWrapper : QObject
{
Q_OBJECT
public:
MockClamWrapper();
~MockClamWrapper();
bool loadDatabase(unsigned int *signatureCount=NULL);
Q_SIGNALS:
void databaseLoaded();
};
MockClamWrapper.cpp
bool MockClamWrapper::loadDatabase(unsigned int *signatureCount){
QThread::currentThread()->sleep(10);
databaseLoaded();
return true;
}
MainWindow.h
#include <QMainWindow>
#include <QFileDialog>
#include "mockclamwrapper.h"
namespace Ui {
class MainWindow;
}
class MainWindow : public QMainWindow
{
Q_OBJECT
public slots:
void enableWindow();
public:
explicit MainWindow(QWidget *parent = 0);
~MainWindow();
private:
Ui::MainWindow *ui;
MockClamWrapper *clam;
void initWindow();
};
MainWindow.cpp
MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)
{
ui->setupUi(this);
connect((QObject*)clam, SIGNAL(databaseLoaded()),(QObject*)this,SLOT(enableWindow()));
QFuture<void> fut = QtConcurrent::run(this,&MainWindow::initWindow);
}
MainWindow::~MainWindow()
{
delete ui;
}
void MainWindow::initWindow(){
clam->loadDatabase(NULL);
}
void MainWindow::enableWindow(){
ui->checkFileButton->setEnabled(true);
}
The program compiles, but it crashes right after start. I assume that I do something wrong with slots and signals, but can't find my mistake.

Answer 1

The reason for crash is that you are not making any instance of the class MockClamWrapper. In the connect statement, you are referencing a pointer that points to nothing. Make a new object and then connect :
clam = new MockClamWrapper();
connect(clam, SIGNAL(databaseLoaded()), this, SLOT(enableWindow()));