Fail to invoke QML function - qt

Question

According to http://doc.qt.io/qt-5/qtqml-cppintegration-interactqmlfromcpp.html chapter "Invoking QML Methods", I try to invoke the bbox function within main.qml from C++.
Here is my code :
main.qml
import QtQuick 2.0
import QtQuick.Window 2.0
import QtLocation 5.6
import QtPositioning 5.6
Window {
width: 512
height: 512
visible: true
Item{
anchors.fill: parent
Plugin{
id: osmplugin
name: "osm"
}
Map {
anchors.fill: parent
id: map
plugin: osmplugin;
zoomLevel: (maximumZoomLevel - minimumZoomLevel)/2
center {
// The Qt Company in Oslo
latitude: 59.9485
longitude: 10.7686
}
}
Component.onCompleted:{
console.log("zoomlevel : " + map.zoomLevel)
console.log("Visible region : " + map.visibleRegion)
}
function bbox(){
return map.visibleRegion;
}
}
}
and main.cpp
#include <QGuiApplication>
#include <QQmlApplicationEngine>
#include <QQuickItem>
#include <QGeoRectangle>
#include <QQmlComponent>
int main(int argc, char *argv[])
{
QGuiApplication app(argc, argv);
QQmlApplicationEngine engine;
QQmlComponent component(&engine, "qrc:/main.qml");
QObject *map = component.create();
QVariant ret;
bool ok = QMetaObject::invokeMethod( map, "bbox", Qt::DirectConnection, Q_RETURN_ARG( QVariant, ret ) );
if ( !ok ){
qWarning( "Fail to call qml method" );
}
QGeoRectangle rect = qvariant_cast<QGeoRectangle>( ret );
return app.exec();
}
I get the following error message :
"QMetaObject::invokeMethod: No such method QQuickWindow::bbox()"
Seems it does not find the bbox function. Could you help me to find the problem ?
Thanks in advance.

Answer 1

Give your item an object name:
Item{
anchors.fill: parent
objectName: "bboxObj"
function bbox(){
return map.visibleRegion;
}
}
In C++ get your Object using the object name:
QObject *map = component.create();
QObject *bboxObj= map->findChild<QObject*>("bboxObj");
and invoke the method:
if (bboxObj)
ok = QMetaObject::invokeMethod( bboxObj, "bbox", Qt::DirectConnection, Q_RETURN_ARG( QVariant, ret ) );