Noob question about Properties and Scopes

radixzz

I'm totally new into the Qt and qml stuff and I just waste my all day trying to understand the property scopes without success. So I have a Table View with an Item delegate like this:

@
TableView {
id: logView
model: logModel
TableViewColumn{
role:"idLog"
}
itemDelegate: Item {
id: logItem
property int idLog: -1
Rectangle {
width:50
height:20
MouseArea{
anchors.fill: parent
onClicked: console.log( parent.parent.idLog) //always -1
//onClicked: console.log( logItem.idLog)
}
}

      Component.onCompleted: {
            if (styleData.role === "idLog"){
               console.log(styleData.value) // 1 and 2
               idLog = styleData.value
         }
      }
  }

Component.onCompleted: {
logModel.append({"idLog":1})
logModel.append({"idLog":2})
}
}
@

And all I want is to save the id into the item prop so I can retrieve it after when I click the rect. I always get -1. Why is that?

sierdzio

See "this":http://qt-project.org/doc/qt-5.0/qtquick/qtquick-modelviewsdata-modelview.html#mouse-and-touch-handling. You should not be saving the stuff in a delegate, as the engine is allowed to create and delete those components as they are needed.

radixzz

Thank you! after proper reading I can see now how nasty is to try saving things in a delegate. So now what I'm doing is to simply access the model directly in this way:

@
onClicked: {
var model = logModel.get(styleData.row)
console.log("idLog",model.idLog) //prints correct id
}
@
But now my question is this: can I expect to have always a correlation between the row and the original object index? I tried removing elements and it seems that the model keeps track correctly but, should I be aware of a better way of doing this? gotchas?

sierdzio

Hm, that is a good question. I don't think you should depend upon it, as it is possible to remove an item from the middle of the list - the index might jump then. But I am not sure. If you have a use case where you are certain the list will not be reordered, and that nothing will be removed from it, I think you can assume the index will stay valid.