How to overload operator<< for qDebug

Question

Hi,

I'm trying to create more useful debug messages for my class where store data. My code is looking something like this

#include <QAbstractTableModel>
#include <QDebug>

/**
  * Model for storing data. 
  */
class DataModel : public QAbstractTableModel {
    // for debugging purposes
    friend QDebug operator<< (QDebug d, const DataModel &model);

    //other stuff
};

/**
  * Overloading operator for debugging purposes
  */
QDebug operator<< (QDebug d, const DataModel &model) {
    d << "Hello world!";
    return d;
}

I expect qDebug() << model will print "Hello world!". However, there is alway something like "QAbstractTableModel(0x1c7e520)" on the output.

Do you have any idea what's wrong?

Answer 1

After an hour of playing with this question I figured out model is pointer to DataModel and my operator << takes only references.