Qt - 没有匹配的函数来调用连接

Question

I have this error when I tried to call connect.

E:\\GraphTool\\graphscene.cpp:7: error: no matching function for call to 'GraphScene::connect(QObject*&, void (MainWindow:: )(Mode), GraphScene , void (GraphScene::*)(Mode))' QObject::connect(parent, &MainWindow::changedMode, this, &GraphScene::setMode);

I called connect in graphscene.cpp

    GraphScene::GraphScene(QObject *parent) : QGraphicsScene (parent), mode(NAV) {
        QObject::connect(parent, &MainWindow::changedMode, this, &GraphScene::setMode);
    }

The GraphScene class :

class GraphScene : public QGraphicsScene {
    Q_OBJECT
public:
    GraphScene(QObject *);
    void mousePressEvent(QGraphicsSceneMouseEvent*);

public slots:
    void setMode(Mode m);

private:
    Mode mode;
}

The MainWindow class :

class MainWindow : public QMainWindow {
    Q_OBJECT

public:
    explicit MainWindow(QWidget *parent = nullptr);
    ~MainWindow();

public slots:
    void actionTriggered(QAction *action);

signals:
    void changedMode(Mode newMode);

private:
    Ui::MainWindow *ui;
    QActionGroup* modesGroup;
    GraphScene *scene;
};

I emit the signal here, I don't know if that have anything to do with it :

 void MainWindow::actionTriggered(QAction *action){
    QString actionText = action->text() ;
    if(actionText == "Navigation"){
        emit changedMode(NAV);
    }
    else if (actionText == "Add node") {
        emit changedMode(ADD_NODE);
    }
    else if (actionText == "Delete node") {
        emit changedMode(DEL_NODE);
    }
}

I found many other answers on SO related but I couldn't fix it. Most tell to check for QObject inheritance and Q_OBJECT macro.

Answer 1

Have you tried sending a MainWindow* to the ctor instead? I think it is failing to map the sender function to its object:

GraphScene::GraphScene(MainWindow *parent)
    : QGraphicsScene (parent), mode(NAV)
{
    QObject::connect(parent, &MainWindow::changedMode, this, &GraphScene::setMode);
}