Qt matching signal with custom slot

Question

I'm trying to use a QAction (QMenu member entry) to open a new window. Precisely: I want actionAbout signal predefined activated to match MainWindow custom slot open AboutWindow - and that's what I've got trouble with.

I know that I can use either the connect Qt function manually inside the source main_window.cpp file or just click it up in the Qt Creator, but my custom slot doesn't show up so I cannot select it. Maybe my slot function declaration is wrong (invalid parameters) and that's why QtCreator doesn't allow me to choose my custom slot in the GUI signals & slots. Could anyone point me what should I do to make QtCreator display my custom slot in the dropdown and how should the connect function call look like?

This is my main_window.h file content:

#include 
#include "about_window.h"

namespace Ui {
    class MainWindow;
}

class MainWindow : public QMainWindow
{
    Q_OBJECT

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

public slots:
   void openAboutWindow();

private:
    Ui::MainWindow *ui;
    Ui::AboutWindow *aboutWindow;
};

And this is main_window.cpp:

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);
    connect(actionAbout, SIGNAL(activated()), this, SLOT(openAboutWindow(this));
}

MainWindow::~MainWindow()
{
    delete ui;
}

void MainWindow::openAboutWindow(QWidget *parent)
{
   aboutWindow = new Ui::AboutWindow(parent); // Be sure to destroy you window somewhere
   aboutWindow->show();
}

The compiler shouts about both constructor and openAbutWindow:

../Application/main_window.cpp: In constructor ‘MainWindow::MainWindow(QWidget*)’:
../Application/main_window.cpp:9:13: error: ‘actionAbout’ was not declared in this scope
../Application/main_window.cpp:9:80: error: expected ‘)’ before ‘;’ token
../Application/main_window.cpp: In member function ‘void MainWindow::openAboutWindow(QWidget*)’:
../Application/main_window.cpp:19:44: error: invalid use of incomplete type ‘struct Ui::AboutWindow’
../Application/about_window.h:7:11: error: forward declaration of ‘struct Ui::AboutWindow’
../Application/main_window.cpp:20:15: error: invalid use of incomplete type ‘struct Ui::AboutWindow’
../Application/about_window.h:7:11: error: forward declaration of ‘struct Ui::AboutWindow’

cmannett85 cmannett85 · Accepted Answer · 2013-01-26T10:33:10

../Application/main_window.cpp:9:13: error: ‘actionAbout’ was not declared in this scope

The error message says it all, where is the QAction defined? Should it be ui->actionAbout?

connect(actionAbout, SIGNAL(activated()), this, SLOT(openAboutWindow(this));

openAboutWindow() does not take any arguments, and regardless this is an instance not a type.

Qt matching signal with custom slot

1 Answers