Today I am going to write about how to serialize any QObject class and then write the object to a byte array and desalinize it back from the byte array. This is crucial if you want to send any object over the net or save it in a file or database.
First, we need a base class which make all of it's subclass serializable.
SerializableClass.h
#ifndef SerializableClass_H_
#define SerializableClass_H_
#include <qt4/QtCore/qobject.h>
#include <qt4/QtCore/qdatastream.h>
class SerializableClass : public QObject
{
Q_OBJECT
public:
explicit SerializableClass(QObject *parent = 0);
};
QDataStream &operator<<(QDataStream &ds, const SerializableClass &obj);
QDataStream &operator>>(QDataStream &ds, SerializableClass &obj) ;
#endif /* SerializableClass_H_ */
SerializableClass.cpp
#include "SerializableClass.h"
#include <qt4/Qt/qvariant.h>
#include <qt4/QtCore/qmetaobject.h>
SerializableClass::SerializableClass(QObject *parent) :
QObject(parent)
{
}
QDataStream &operator<<(QDataStream &ds, const SerializableClass &obj) {
for(int i=0; i<obj.metaObject()->propertyCount(); ++i)
{
if(obj.metaObject()->property(i).isStored(&obj))
{
ds << obj.metaObject()->property(i).read(&obj);
}
}
return ds;
}
QDataStream &operator>>(QDataStream &ds, SerializableClass &obj) {
QVariant var;
for(int i=0; i<obj.metaObject()->propertyCount(); ++i)
{
if(obj.metaObject()->property(i).isStored(&obj))
{
ds >> var;
obj.metaObject()->property(i).write(&obj, var);
}
}
return ds;
}
Now, you need to extend this class to make your class serializable. Let's see as example.
Student.h
#ifndef STUDENT_H_
#define STUDENT_H_
#include "SerializableClass.h"
class Student : public SerializableClass
{
Q_OBJECT
Q_PROPERTY(int id READ getId WRITE setId)
Q_PROPERTY(QString Name READ getName WRITE setName)
public:
Student();
int getId() const { return id; }
void setId(int newId) { id = newId; }
QString getName() const { return Name; }
void setName(const QString &newName) { Name = newName; }
private:
int id;
QString Name;
};
#endif /* STUDENT_H_ */
Student.cpp
#include "Student.h"
Student::Student()
{
}
Here Q_OBJECT, Q_PROPERTY macros are required to take care of generating proper metaObject for your class. Now we are going to put these classes in action at main() function.
main.cpp
Q_DECL_EXPORT int main(int argc, char **argv)
{
Student G;
Student G2;
G.setId(30);
G.setName("pervez");
qDebug()<<G.getId()<<G.getName();
QByteArray byteArray;
QDataStream out(&byteArray, QIODevice::WriteOnly);
out <<G;
qDebug()<<G2.getId()<<G2.getName();
QDataStream in(byteArray);
in >> G2;
qDebug()<<G2.getId()<<G2.getName();
Application app(argc, argv);
new ApplicationUI(&app);
return Application::exec();
}
Here QDataStream out writes the G object in byteArray at "out <<G;" statement. that's why we use >> and << operator in SerializableClass.h header file
