Problems to access private variables of subclass.

[AdrianCruz]

Hello friends. I have a QWidget in that i have a subclass of qgraphicsScene. In my QGraphicsScene I open a file to write it and i want to close this file with a Push buttom in my QWidget. I am trying to pass the file since my subclass qgraphicsscene to the qwidget, but i receive the next message :

C:\Qt\5.10.0\mingw53_32\include\QtCore\qfile.h:150: error: 'QFile::QFile(const QFile&)' is private
Q_DISABLE_COPY(QFile)

I have tried to do it with friends class but i am not be able to. My code:

#include <QFileInfo>
#include <QMessageBox>
#include <QTextStream>
#include <QList>

class subQLabel;
class subQGraphicsScene;

namespace Ui {
class interfazMatrizExperto;
}

class interfazMatrizExperto : public QWidget
{
    Q_OBJECT

public:
    explicit interfazMatrizExperto(const QString rutaImagenFondo, const QString matrizExpertoFile,int nFil,int nCol,QWidget *parent = 0);
    ~interfazMatrizExperto();

    friend class subQGraphicsScene;


protected:
    void resizeEvent(QResizeEvent *evt);
private slots:
    void on_cargarImagenBottom_clicked();

    void on_deshacerbottom_clicked();

    void on_comebackbottom_clicked();

    void showEvent(QShowEvent *);

    void on_terminarBottom_clicked();


private:
    Ui::interfazMatrizExperto *ui;
    subQLabel *labelImage;
    subQGraphicsScene *scene;
    QString imagen;
    int numCol;
    int numFil;
    QString rutaFicheroExperto;


};
///////////////////////////////////////////////////////////////////////////////////////////////////////



class subQLabel : public QLabel
{
    Q_OBJECT

public:
    subQLabel(QWidget* parent);
    ~subQLabel();
    void mousePressEvent(QMouseEvent *event) override;
};



//////////////////////////////////////////////////////////////////////////////////////////////////////////

class subQGraphicsScene : public QGraphicsScene
{
    Q_OBJECT

public:
    subQGraphicsScene(const QString rutaFichero, QWidget* parent);
    ~subQGraphicsScene();
    inline void setNumFil(const int nFil) { numFil = nFil;}
    inline void setNumCol(const int nCol) { numCol = nCol;}
    inline void setWidth(const int sizeWidth) { width = sizeWidth;}
    inline void setHeight(const int sizeHeight) { height = sizeHeight;}
    inline QFile getFile()const { return file;}

protected:
    void mousePressEvent(QGraphicsSceneMouseEvent *event);

private:
    QFile file;
    int count=0;
    int numFil;
    int numCol;
    int width;
    int height;
    QTextStream stream;
};

#endif // INTERFAZMATRIZEXPERTO_H

void interfazMatrizExperto::on_terminarBottom_clicked()
{
    QFile file = scene->getFile();
    file.close();
    close();

}

[JonB]

@AdrianCruz
We could make this work, if we really wanted. But it doesn't seem like the right approach: you shouldn't need to pass QFile open/closes across widget boundaries. Why don't you re-architect to store, open & close the QFile within one class, and as a side-effect your problem will go away?

[AdrianCruz]

@JonB Because i am using my class SubQGraphicsScene to store the mouse position event and when you push the buttom is when i finish to gather the position.

Which will it be the best option to do that?

[JonB]

@AdrianCruz
Given your way of doing it, pass around a QFile & instead of a QFile. Something like:

inline QFile& getFile()const { return file;}

QFile& file = scene->getFile();

But this is not the best way to arrange things. Provide a close-file method in the scene to call from the interface, or better send the scene a signal to do so.

[AdrianCruz]

@JonB that doesn't solve the problem because the problem is about private variables.

I will try to do in other way.

[JonB]

@AdrianCruz
No, your problem is not about private variables. It's about not being able to copy a QFile. Did you try what I suggested?
EDIT I did miss out an &. I have corrected my suggestion. I am not a native C++-er. The principle is: you can pass references (or pointers to) QFiles around, but you cannot pass a plain QFile because that would require copy.