Enumerate all objects in QQmlEngine - c++

Question

I want to enumerate all the objects (derived from QObject) existent and newly created in QQmlApplicationEngine. The main goal it to execute the following lines of code for each of them:
void denominate(QObject * const object)
{
if (object->objectName().isEmpty()) {
object->setObjectName(object->metaObject()->className());
}
}
It is needed to distinct some of the objects in QML runtime. Say, when StackView items are created from Components and I want to know which of them is really on the top.
Creation of some of components or C++ classes are delayed. And if I get a root objects and enumerate children() of them, it is a half of the solution. Also there is QQmlApplicationEngine::objectCreated signal, but I don't fully understand interrelation between contexts, engine and (root) objects.
How to name all the unnamed objects, which lives into QQmlEngine?

Answer 1

You can rename all of them using recursive enumeration
For example:
QML file:
import QtQuick 2.6
import QtQuick.Window 2.2
Window {
visible: true
width: 640
height: 480
title: qsTr("Hello World")
MouseArea
{
id: r1
width: 200
height: 200
}
Rectangle
{
id: r2
color: "green"
width: 100
height: 100
Item
{
id: r3
width: 50
height: 50
}
}
}
You can set their names in the c++ part using the next mechanism:
void changeNames(QList<QObject*> ch)
{
for( QObject* ob: ch)
{
if (ob->objectName().isEmpty())
{
ob->setObjectName(ob->metaObject()->className());
}
changeNames( ob->children() );
}
}
void enumerate(QList<QObject*> ch)
{
for( QObject* ob: ch)
{
qInfo() << ob->objectName();
enumerate( ob->children() );
}
}
int main(int argc, char *argv[])
{
QGuiApplication app(argc, argv);
QQmlApplicationEngine engine;
engine.load(QUrl(QStringLiteral("qrc:/main.qml")));
QObject *rootObject = engine.rootObjects().first();
changeNames(rootObject->children());
enumerate(rootObject->children());
return app.exec();
}
You will see the next names in the output:
"QQuickRectangle"
"QQuickMouseArea"
"QQuickItem"
If you have to add new component dynamically you can repeat this procedure, or find necessary component and rename it