CODEWITHSUNDEEP
c++qtfunctionvirtualabstract
user1784297
user1784297

Reputation: 105

Cant declare a QWidget because virtual functions are pure

I'm trying to make use of interfaces in Qt/C++, but I keep getting a compile error which makes no sense to me, because I have implemented the virtual functions in the derived class. So I was hoping for some help :) Oh yeah, and the compile error is "cannot declare variable 'w' to be of abstract type 'Widget' because the following virtual functions are pure within 'Widget': startGame(), getBoard(), gameFinished().

Main.cpp 

#include "widget.h"
#include <QApplication>
int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    Widget w;
    w.show();
    return a.exec();
}

ADTType.h

#ifndef ADTTYPE_H
#define ADTTYPE_H
class ADTType
{
public:
    virtual void startGame() = 0;
    virtual void getBoard() = 0;
    virtual void gameFinished() = 0;
    virtual ~ADTType() {}
};
Q_DECLARE_INTERFACE(ADTType, "ADTType")
#endif // ADTTYPE_H

Widget.h

#ifndef WIDGET_H
#define WIDGET_H

#include <QWidget>
#include <QSignalMapper>
#include <QHBoxLayout>
#include <QPushButton>
#include "ADTType.h"

class Widget : public QWidget,
        public ADTType
{
    Q_OBJECT
    Q_INTERFACES(ADTType)

public:
    explicit Widget(QWidget *parent = 0);
    ~Widget();

private:
    QHBoxLayout * mainLayout;
    QPushButton * startButton;
    QPushButton * buttons[10];
    QSignalMapper * map;
};
#endif // WIDGET_H

Widget.cpp

#include "widget.h"
#include "ui_widget.h"

Widget::Widget(QWidget *parent) :
    QWidget(parent)
{}

Widget::~Widget()
{}
void Widget::startGame() {
    for (int i = 0; i < 10; i++) {
             buttons[i]->setStyleSheet("QPushButton {background-color: normal}");
    }
    setButtons(true);
    startButton->setDisabled(true);
}

void Widget::getBoard() {

    bool * cells = game->getCells();
    for (int i = 0; i < 10; i++) {
        if (!cells[i]) {
             buttons[i]->setStyleSheet("QPushButton {background-color: red}");
             buttons[i]->setEnabled(false);
        }
    }
}

void Widget::gameFinished() {

    int answer = game->getAnswer();
    buttons[answer]->setStyleSheet("QPushButton {background-color: green}");
    setButtons(false);
    game->reset();
    QMessageBox::information(this,tr("Finito"),tr("You found it."),
                             QMessageBox::Ok);
    startButton->setEnabled(true);
 }

Upvotes: 0

Views: 629

Answers (2)

Ashot Khachatryan
Ashot Khachatryan

Reputation: 2376

You derived ADTType abstract class from the Widget so you need to override pure virtual functions in the Widget class otherwise it also will become abstract.

class Widget : public QWidget,
     public ADTType
{
  ...
  void startGame() { ... }
  void getBoard() { ... }
  void gameFinished() { ... }
};

Upvotes: 1

vsoftco
vsoftco

Reputation: 56567

class Widget : public QWidget,
    public ADTType

So Widget inherits from the abstract class ADTType. However, you don't declare the overrides (startGame() etc) in your Widget class, but you only define them in the Widget.cpp file. You also need to declare them in the Widget.h class header

// need these declarations inside the class Widget in Widget.h
virtual void startGame();
virtual void getBoard();
virtual void gameFinished();

Minimal example here.

Upvotes: 3

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