What is the order of Component.onCompleted in a QML file with many items?

Question

For example, consider the code below:

Rectangle {
    id: idRectParent

    Rectangle {
        id: idRectChild1
        component.onCompleted: {
            console.log("Iam Child 1")
        }
    }

    Rectangle {
        id: idRectChild2
        component.onCompleted: {
            console.log("Iam Child 2")
        }
    }

    component.onCompleted : {
        console.log("Iam parent Rect")
    }
}

I'm getting the output below if I run it in qmlscene (I have tried almost 50 times).

Iam parent Rect
Iam Child 2
Iam Child 1

Why is the output in the above order, instead of:

Iam parent Rect
Iam Child 1
Iam Child 2

or

Iam Child 1
Iam Child 2
Iam parent Rect

or any other combination.

Answer 1

The order is undefined:

Emitted after component "startup" has completed. This can be used to execute script code at startup, once the full QML environment has been established.

The corresponding handler is onCompleted. It can be declared on any object. The order of running the onCompleted handlers is undefined.

http://qt-project.org/doc/qt-5/qml-qtqml-component.html#completed-signal