QML-How-to? Anonymous Access To TableView From Within Delegates

wahynes

Hi,

Using QML, I'm writing a custom itemDelegate and rowDelegate that I want to be able to
use across any number of different TableView instances.

As the code to follows shows, I've been able to accomplish this--but only in a way that I'm
extremely dubious about it working in future (or previous, for that matter) releases of Qt.
I'm currently using Qt 5.2.

@
Component {
id: tableRowDelegate

Rectangle {
height: 16
color: styleData.selected ? "#448" : (styleData.alternate? "#eee" : "#fff")

     property TableView tableView

    Component.onCompleted: {
          if (styleData.row > -1)  // Not entirely sure why this is needed -- worse, I don't know why it works; it just does
                tableView = parent.parent.parent.parent.parent.parent.parent.parent
    }

 // Other delegate code omitted for brevity

}
}

Component {

id: tableCellDelegate

Rectangle {
    width: parent.width
    height: parent.height
    color: "transparent"
    border.color: "#a3b3b3"
    border.width: 1
    radius: 5

    property TableView tableView

    Component.onCompleted: {
        tableView = parent.parent.parent.parent.parent.parent.parent.parent.parent
    }

 // Other delegate code omitted for brevity
}

}
@

Once these delegates are constructed, access to the enclosing TableView is trivial
(and anonymous) by prefixing the property name with 'tableView.'; i.e.
@
tableView.alternatingRowColors
@

just for example.

Is there really no better way to access the view from within a delegate without
hard-coding the ancestry, or worse: without hard-binding explicitly to the id of
the TableView?

Thanks for any thoughts!

wahynes

Jens

Your observation is correct and I think this is a valid issue.

In a ListView delegates can access the "ListView" attached property to get access to the View. For technical reasons I don't think we can attach a TableView property in exactly the same manner but there should still be a similar attached property available to delegates.

Perhaps you could file a suggestion with a title such as:
"Provide a way way to access the view from inside a TableView delegate". So that we can track this.

As far as workarounds goes, you are correct that the parent hierarchy is likely to change in future versions. In fact I believe it will change already in 5.3 due to performance optimizations. A slightly more reliable way would be to create a simple loop that iterates up the parent hierarchy until it hits an object that has Accessible.role === Accessible.Table or similar.

wahynes

Thanks, Jens,

I posted this same question on StackOverflow. A couple of suggestions
from one commenter, (plus about 10 hours of banging my head against
my keyboard) and I actually came up with a fairly painless way to achieve
this that avoids using the id AND avoids making any assumptions
about the internal ancestry of a delegate.

Rather than duplicating the solution here, you can read about it there:
"Anonymous Access To TableView.":http://stackoverflow.com/questions/23522186/qml-how-to-anonymously-access-to-tableview-from-within-delegates:

It's not quite as straightforward as the exposure of the model to the
delegate, but it's pretty close.

wahynes