j2doll/qt-polymorphism.md

## qt-polymorphism.md

      
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              qt-polymorphism.md
            
          
    Qt Polymorphism

a


a.h

#ifndef A_H
#define A_H
#include <QtGlobal>
#include <QObject>

class A : public QObject
{
   Q_OBJECT
  public:
  A(QObject* parent = NULL);
};

#endif // A_H

a.cpp

#include "a.h"

A::A(QObject* parent)
 : QObject(parent)
{
}
b


b.h

#ifndef B_H
#define B_H
#include <QtGlobal>
#include <QObject>
#include "A.h"

class B : public A
{
  Q_OBJECT
 public:
  B(QObject* parent = NULL);
};

#endif // B_H

b.cpp

#include "b.h"

B::B(QObject* parent)
 : A(parent)
{
}
main


main.cpp

#include <cstdio>
#include <string>
#include <QtCore/QCoreApplication>
#include <QDebug>
#include "a.h"
#include "b.h"

int main(int argc, char *argv[])
{
  QCoreApplication a(argc, argv);

  QObject *obj = new B; // polymorphism in object-oriented programming
  qDebug() << QString( obj->metaObject()->className() ); // print "B"
  
  return 0;
}