QML : anchors.verticalCenter does not work

[cosmoff]

Hello everyone,
I show you my code, It will be easier to explain my problem.

Window {
    id : windowId
    visible: true
    width: 640
    height: 480
    title: qsTr("Hello")
    color :"grey"

   Rectangle{
       id : myButton
       width : 100
       height : 100
       color : "green"
       anchors.verticalCenter: windowId.verticalCenter
}
}

If I replace windowId by parent it works but I do not understand why ? It should work with id from my window

Can you explain what is wrong.

thanks a lot

[raven-worx]

@cosmoff
because the Window is not an item actually. it has a contentItem (default property, which gets the child items reparented to). So use this property, or even better, simply use parent