QML property weak reference?

Evgeniy Dushistov

I created object with Qt.createComponent , saved reference to property and then I called destroy for object in onClosed signal handler.
And what I can not understand is why property becomes null after destroyed without manually setting to null.
I thought that property is "strong reference", so even after destroying it will hold reference to some kind of "zombie" until I set it to null manually, but looks like property is some kind of "weak reference"?

ApplicationWindow {
       id: applicationWindow
      property MyPopup dlg: null
      
     function show() {
        const comp = Qt.createComponent("qrc:/MyPopup.qml");
        const params = {parent: applicationWindow.contentItem};
        applicationWindow.dlg = comp.createObject(params.parent, params);
        console.assert(applicationWindow.dlg !== null, "MyPopup creation failed");
        applicationWindow.dlg.open();
    }

Popup {
    onClosed: {
        console.log("onClosed was called", view);
        view.destroy();
    }

jeremy_k

@Evgeniy-Dushistov I had not noticed that previously, and there's no obvious mention of it in the documentation. Thanks! I see the same thing with this code:

import QtQuick 2.15
import QtQuick.Window 2.15

Window {
    id: root

    property Rectangle myRect

    Component {
        id: myComponent
        Rectangle { color: "yellow" }
    }

    MouseArea {
        anchors.fill: parent
        onClicked: {
            if (loader.status == Loader.Null) {
                loader.sourceComponent = myComponent;
                myRect = loader.item;
            }
            else {
                loader.sourceComponent = null;
            }
        }
    }

    Loader {
        id: loader
        anchors.fill: parent
    }

    Text { anchors.centerIn: parent; text: "myRect: " + root.myRect }
}

My guess is that the properties that hold a QObject are tracked with a QPointer, but I'm not familiar enough with the implementation to find the answer quickly.