Error: Cannot assign to non-existent property

[wysota]

Does it work if you assign the value in Component.onComplete handler of the Zero element?

[ustulation]

Does it work if you assign the value in Component.onComplete handler of the Zero element?

Yes it does.

Could you tell me why? m_ref is already well formed when Zero {} is used in main.qml (which is why I can use any property which is present in Rectangle before its addition as a subObject inside Zero.qml.)

[wysota]

m_ref is already well formed when Zero {} is used in main.qml

Apparently, it is not. Properties are assigned as the parser goes through the definition. Since the internal object has not yet been fully initiated (meaning that its custom properties are not yet created) the binding fails.