/* main.cpp */

#include <QCoreApplication>
#include "runner.h"

int main(int argc, char *argv[])
{
    QCoreApplication a(argc, argv);
    Runner *runner = new Runner;
    runner->start();
    return a.exec();
}

/* ifoo.h */

#ifndef IFOO_H
#define IFOO_H

#include <QObject>

class IFoo
{
public:
    virtual void fooMethod() = 0;
    virtual void fooSlot() = 0;
    virtual void fooSignal() = 0;
};
Q_DECLARE_INTERFACE(IFoo, "ifoo/1.0")
#endif // IFOO_H


/* runner.h */
#ifndef RUNNER_H
#define RUNNER_H

#include <QObject>
#include <QDebug>
#include "ifoo.h"

class Runner : public QObject, public IFoo
{
    Q_OBJECT
    Q_INTERFACES(IFoo)
public:
    Runner(QObject * parent = 0) : QObject(parent)
    {
    }

    void start()
    {
        qDebug() << "start";
        IFoo *runner = new Runner;
        //ideally I would love this to work:
        ////connect(runner, SIGNAL(fooSignal()), this, SLOT(fooSlot()))
        //that is, the interface would declare signals and slots
        //technically it's possible, see this article: http://doc.qt.digia.com/qq/qq15-academic.html#multipleinheritance (by using composition instead)
        //but it does not provide all the code that I could run and test and I can't get it right.

        //qobject_cast<Runner*>(runner) fails here, static_cast works
        connect(static_cast<Runner*>(runner), SIGNAL(fooSignal()), this, SLOT(fooSlot()));
        runner->fooMethod();
    }
    void fooMethod()
    {
        qDebug() << "fooMethod called";
        qDebug() << "emitting fooSignal";
        emit fooSignal();
    }

public slots:
    void fooSlot()
    {
        qDebug() << "fooSlot called";
    }

signals:
    void fooSignal();
};

#endif // RUNNER_H