Обращение к уже существующему классу

class MyClass :public QObject{
public: MyClass(QObject *parent):QObject(parent){}
public: void someFunc(){
       QObject * parentClass = parent();  //get parent for current class
       MyParentClass * pClass = qobject_cast<MyParentClass *>(parentClass); //cast QObject * to ParentClass
       if(pClass == NULL)
          return;
   }
};

#ifndef PORTSCAN_H
#define PORTSCAN_H
 
#include <QObject>
#include "frontwindow.h"
#include "QTcpSocket"
 
 
class PortScan : public QObject
{
    Q_OBJECT
public:
    explicit PortScan(QObject *parent = 0);
signals:
    
public slots:
    
private:
};
 
#endif // PORTSCAN_H

#include "portscan.h"
 
PortScan::PortScan(QObject *parent) :
    QObject(parent)
{
}

#include "portscan.h"
 
PortScan::PortScan(QObject *parent) :
    QObject(parent)
{
}
//-------------------------------------------------------------------
void PortScan::start(QString &IP, int &StartPort, int &EndPort){
    FrontWindow f;
    QString out = "Scan started!\n\n";
    int tempPort = StartPort;
 
    qDebug() << out;
    f.AppendToPortOut(out);
    socket = new QTcpSocket(this);
 
    while(tempPort<=EndPort){
 
        socket->connectToHost(IP, tempPort);
 
        if(socket->waitForConnected()){
            out = QString("%1 has opened port: %2").arg(IP).arg(tempPort);
            qDebug() << out;
            f.AppendToPortOut(out);
 
            socket->close();
 
        }
        tempPort++;
    }
    delete socket;
 
    out = QString("\nScan finished!");
    qDebug() << out;
    f.AppendToPortOut(out);
}

#include <iostream>
...
using namespace std;