I am getting the following error when I try to access bins private member of the GHistogram class from within the extractHistogram() implementation:

error: 'QVector<double> MyNamespace::GHistogram::bins' is private
error: within this context

Where the 'within this context' error points to the extractHistogram() implementation. Does anyone knows what's wrong with my friend function declaration?

Here's the code:

namespace MyNamespace{

class GHistogram
{

public:
    GHistogram(qint32 numberOfBins);
    qint32 getNumberOfBins();

    /**
     * Returns the frequency of the value i.
     */
    double getValueAt(qint32 i);
    friend GHistogram * Gbdi::extractHistogram(GImage *image, qint32 numberOfBins);

private:
    QVector<double> bins;
};

GHistogram * extractHistogram(GImage * image, qint32 numberOfBins);

}