Thanks for reply. i do know the 'object' is from the QmlObjectListModel, and it is one of the "roles", as you said. But i can't find where this 'object' declare, i am a C/C++ programer, usually, if there is a var, you should declare it first, then use it. for this 'object' we talk about, i can't trace the position where it declare! , can you tell me the reason, or some clue? thanks.