int main(int argc, char *argv[])
{
    QGuiApplication app(argc, argv);

    qmlRegisterType<A>("test.test.A", 1, 0, "A");
    qmlRegisterType<B>("test.test.A", 1, 0, "B");
    qmlRegisterType<C>("test.test.A", 1, 0, "C");

    QQmlApplicationEngine engine;
    engine.load(QUrl(QStringLiteral("qrc:/qml/desktop/main.qml")));

    return app.exec();
}

namespace Ui {
    class form;
}

class MainWindow : public QMainWindow
{
    Q_OBJECT

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

private:
    Ui::form *ui;
};

#include "mainwindow.h"
#include "ui_form.h"

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

MainWindow::~MainWindow()
{

}