类之间的QT连接

Question

I think i have some troubles getting this right: I have a QMainWindow class. In my programm I want to create other classes eg for input handling, computation...

Now first from my mainwindow class i want to send to my fileselector (file handler) class to open a file dialog, thus save the selected files internally. Unfortunately I am having troubles to connect the slots.

main window:

MA_FEX::MA_FEX(QWidget *parent)
    : QMainWindow(parent), fileSelector(this)

{
    ui.setupUi(this);
    //this works:
    fileSelector.openFiles(this); 
    //this doesn't:
    connect(ui.actionOpenFiles, SIGNAL(triggered()), fileSelector, SLOT(openFiles(this)));
}

MA_FEX::~MA_FEX()
{  
}

mainwindow header:

class MA_FEX : public QMainWindow
{
    Q_OBJECT

public:
    MA_FEX(QWidget *parent = 0);
    ~MA_FEX();

private:
    Ui::MA_FEXClass ui;
    FileSelection fileSelector;
};

file coordination class:

FileSelection::FileSelection(QObject *parent)
    : QObject(parent)
{
}

FileSelection::~FileSelection()
{
}

void FileSelection::openFiles(QWidget *parent){

    QStringList files = QFileDialog::getOpenFileNames(
                         parent,
                         "Select one or more files to open",
                         "c:",
                         "Images (*.csv *.txt )");

}

header:

class FileSelection : public QObject
{
    Q_OBJECT

public:
    FileSelection(QObject *parent);
    ~FileSelection();

public slots:
    void openFiles(QWidget *parent);

private:

};

Am I missing something ? Executing i get Error C2664 on the connect line saying that Parameter 3 'FileSelection' cannot be converted to 'const QObject'.

Answer 1

Look at the declaration of the QObject::connect :

QObject::connect(const QObject * sender, const char * signal,
                 const QObject * receiver, const char * method,
                 Qt::ConnectionType type = Qt::AutoConnection);

It takes pointers, so you need to pass a pointer to fileSelector .

Another problem there is incompatible SIGNAL and SLOT. The slot specification in connect is declaration, so you cannot pass arguments as you did with this . If you use Qt 5 and C++11 you can do that by passing lambda instead of slot specification:

QObject::connect(ui.actionOpenFiles, &QAction::triggered, 
                [this]() { fileSelector.openFiles(this); });

For Qt 4 you need to create wrapping slot in your MA_FEX class which takes no arguments and which will invoke the slot of the fileSelector :

class MA_FEX {
  ...
  Q_SLOT void openFileSelector() { fileSelector.openFiles(this); }
  ...
public:
  MA_FEX(QWidget *parent) : QMainWindow(parent), fileSelector(this) {
    ui.setupUi(this);
    connect(ui.actionOpenFiles, SIGNAL(triggered()), SLOT(openFileSelector()));
  }
  ...
};