QML bindings and scope

rosetter

Hi all,

So I'm thoroughly confused about how scope works in qml. Here's a little test:

@
import QtQuick 2.0

Rectangle {
width: 640/2
height: 1136/2

Item {
width: parent.width
height: parent.height

Image {
id: viewDummy
anchors.fill: parent
source: "viewDummy.png"

ListModel {
id: comments
ListElement {
modelData: "comment 1a"
}
ListElement {
modelData: "comment 1b"
}
}
}

ListView {
anchors.fill: parent

model: viewDummy.comments

delegate: Rectangle {
height: 25
width: 100
Text { text: modelData }
}
}
}
}
@

The above does not display the contents of the model "comment 1a" and "comment 1b". However, if I change "viewDummy.comments" to just "comments" they are displayed..

I would expect the reverse to be true... why can the ListView "see" the ListModel that's wrapped in the Image "viewDummy"? Does the nesting not affect scope?

Thanks for any advice!

Tyler

sierdzio

Within a single QML file, ids are just that: IDs. You don't need to specify the "parent" ID, they are sort of global (but, again: only within this QML file).

By specifying parent.something, you can refer to properties of that parent, like parent.width.

rosetter

IDs are global within a file?! That's a good one to have straight... thanks!

chrisadams

Hi,

Actually, ids are unique within a component scope. In most cases, this means "within a file" (since a QML document is a QML type definition which can be instantiated via a component, and thus a given instantiation of the type has its own component scope), but there are some subtleties.

See http://doc-snapshot.qt-project.org/qt5-stable/qtqml-syntax-objectattributes.html#the-id-attribute and http://doc-snapshot.qt-project.org/qt5-stable/qtqml-documents-scope.html for more information. Delegates are interesting, because they implicitly define a component scope.

Cheers,
Chris.