Question

i have a Controls class that have default constructor and copy constructor and other constructor ,and an assignment operator , and i want to create array of my class using vector . When i resize my vector i get the objects initialized correctly ; but when i want to create my objects using non default constructor i get this error ,

pure virtual method called
terminate called without an active exception

Controls.h

class Controls : public QObject
{

private:

    QHBoxLayout Layout ;
    string Controlname;
    std::auto_ptr<QLabel> Label ;
    std::auto_ptr<QSlider> Slider ;
    std::auto_ptr<QSpinBox> Spin ;

public:

    Controls(QLayout &Parent , string name , const int &Default_value);
    Controls(const Controls &copy);
    Controls();
    ~Controls();

    QLabel *const Get_Label()const { return Label.get() ; }
    QSlider *const Get_Slider()const { return Slider.get() ; }
    QSpinBox *const Get_Spin()const { return Spin.get() ; }
    QHBoxLayout *const Get_Layout() {return &Layout;}

    void SetValue(const int &newvalue);

    Controls &operator= (const Controls &copy);


};

Controls.cpp

Controls &Controls::operator= (const Controls &copy)
{
    Label = std::auto_ptr<QLabel> ( new QLabel() ) ;
    Slider = std::auto_ptr<QSlider> ( new QSlider() ) ;
    Spin = std::auto_ptr<QSpinBox> ( new QSpinBox() ) ;

    Slider->setValue(copy.Get_Slider()->value());
    Slider->setOrientation(Qt::Horizontal);
    Label->setText(QString ("unamed"));
    Spin->setValue(copy.Get_Spin()->value());


    Layout.addWidget(Label.get() , 0 , 0);
    Layout.addWidget(Slider.get() , 0 , 0);
    Layout.addWidget(Spin.get() , 0 , 0);

    QObject::connect(Slider.get() , SIGNAL(valueChanged(int) ) , Spin.get() , SLOT(setValue(int)));
    QObject::connect(Spin.get() , SIGNAL(valueChanged(int) ) , Slider.get() , SLOT(setValue(int)));


    return *this ;
}
Controls::Controls(const Controls &copy)
{
    *this = copy ;
}
Controls::Controls()
{

    Label = std::auto_ptr<QLabel> ( new QLabel() ) ;
    Slider = std::auto_ptr<QSlider> ( new QSlider() ) ;
    Spin = std::auto_ptr<QSpinBox> ( new QSpinBox() ) ;

    Slider->setValue(0);
    Slider->setOrientation(Qt::Horizontal);
    Label->setText(QString ("unamed"));
    Spin->setValue(0);


    Layout.addWidget(Label.get() , 0 , 0);
    Layout.addWidget(Slider.get() , 0 , 0);
    Layout.addWidget(Spin.get() , 0 , 0);

    QObject::connect(Slider.get() , SIGNAL(valueChanged(int) ) , Spin.get() , SLOT(setValue(int)));
    QObject::connect(Spin.get() , SIGNAL(valueChanged(int) ) , Slider.get() , SLOT(setValue(int)));
}
Controls::Controls(QLayout &Parent , string name , const int &Default_value)
{
    Controlname = name ;

    Label = std::auto_ptr<QLabel> ( new QLabel() ) ;
    Slider = std::auto_ptr<QSlider> ( new QSlider() ) ;
    Spin = std::auto_ptr<QSpinBox> ( new QSpinBox() ) ;

    Slider->setValue(Default_value);
    Slider->setOrientation(Qt::Horizontal);
    Label->setText(QString (name.c_str()));
    Spin->setValue(Default_value);


    Layout.addWidget(Label.get() , 0 , 0);
    Layout.addWidget(Slider.get() , 0 , 0);
    Layout.addWidget(Spin.get() , 0 , 0);

    QObject::connect(Slider.get() , SIGNAL(valueChanged(int) ) , Spin.get() , SLOT(setValue(int)));
    QObject::connect(Spin.get() , SIGNAL(valueChanged(int) ) , Slider.get() , SLOT(setValue(int)));

    Parent.addItem(&Layout);

}

void Controls::SetValue(const int &newvalue)
{
    Slider.get()->setValue(newvalue);
}
Controls::~Controls()
{

}

main.cpp
……
.

   vector <Controls> i ;
      i.resize(2 ); // this is work 

     i.push_back(Controls(layout , "WHITE_BALANCE_RED_V" ,12);// this is not working 

Answer 1

This has nothing to do with std::vector and non-default constructors.
You did not provide the whole code, but I assume this is the continuation of the previous question.

Your Controls::operator= is invalid, it creates copies of QWidgets, and puts them into brand new QLayout. Controls object that you pass to push_back is temporary object that is destroyed after the call and it’s copy is put into vector. But destroyed object’s QWidget members are put into QLayout, which is not destroyed and which is added to the widget you try to show (Panel). After temporary Controls object is destroyed, Panel->show() calls Panel’s QLayout methods that try to access already deleted widgets.

Do you really need to save copies of your Controls objects in your vector? If you store pointers, that would get rid of your problem. Why do you need that vector at all?

And once again, do not use auto_ptr, it’s deprecated and you don’t need it to correctly manage deletion of QObjects.