class Network
{
  Network() {}
  ~Network() {}
  virtual void callMessage() { this->callMessage(); }
  virtual void message() { qDebug() << "Network::message();" }
};

class QMLNetwork : public QObject, public Network
{
public:
    Q_OBJECT

public:
    QMLNetwork(QObject *parent = 0);
    ~QMLNetwork();

    Q_INVOKABLE void callMessage() { QMetaObject::invokeMethod(this, "message");}
    Q_INVOKABLE void message() { qDebug() << "Network::message();"; }

};

QML

import myapi

QMLNetwork
{
  id: myNetwork
  function message() {console.log("network"); }
}