Connecting C++ with QML using Q_INVOKABLE

Question

I have a Qt function:

void MainWindow::button_clicked(Qstring a, Qstring b, Qstring c, Qstring d)

I collect data from QML and I want to pass data to this function which is in Qt. So I know I need to use Q_INVOKABLE but don't know really how to use it.

And one more thing is it possible to invoke some other function when invoke this certain above.
For example: I invoke the above function but in her body I invoke refresh() function. Is this possible?

Solution

To be able to call a method from QML, you must either mark it with Q_INVOKABLE or as a slot. I prefer Q_INVOKABLE if it's not meant to be used as a slot, as its more minimal.

class MainWindow : public QMainWindow {
    Q_OBJECT
public:
...
    Q_INVOKABLE void buttonClicked( const QString& a, const QString& b, const QString& c, const QString& d );
....
};

void MainWindow::buttonClicked( const QString& a, const QString& b, const QString& c, const QString& d ) {
   ...do stuff
   update(); //example
}

The implementation of buttonClicked() can contain any C++ code.

To make the main window instance accessible from QML, you must register it, e.g.

QDeclarativeView* view = ...your view
view->rootContext()->setContextProperty( "_mainWindow", mainWindow );

Once registered, you can call buttonClicked from QML:

_mainWindow.buttonClicked("foo", "bar", "c", "d")

Comments

[user123_456]

hi I have this in mainwindow.cpp : QDeclarativeView *view= new QDeclarativeView; ui->setupUi(this); setCentralWidget(view); QDeclarativeContext *ctxt = view->rootContext(); ctxt->setContextProperty("myModel", QVariant::fromValue(MainWindow::dataList)); view->setSource(QUrl("qrc:/gui.qml")); view->setResizeMode(QDeclarativeView::SizeRootObjectToView); so how to put your line inside? In main.cpp I only create mainwindow and call show method.

[Frank Osterfeld]

It probably would be ctxt->setContextProperty( "_mainWindow", this ); then.

[Frank Osterfeld]

Akiva: With "registering" I meant setting it as context property on the root context, as done in the snippet that follows above.