QML ListModel and custom function property - qml

Question

I want to write tuned version of TableView (TableView.qml in Qt package).
I have ColumnDescriptor.qml with column definition:
Item {
property string title
property var formatDelegate: null
.... (other property definition)
function format(val) {
if (formatDelegate != null)
return formatDelegate(val);
else
return val;
}
}
The above code defines set of properties and fuction format(val), that calls for format value if formatDelefate was set.
In the main table I use list to store predefined columns definition (temporaly) and ListModel to store final columns definition ( the latter is more useful than list in remaining implementation)
list example:
property list<ColumnDescriptor> colDefines: [
ColumnDescriptor {
title: qsTr("col1")
},
ColumnDescriptor {
title: qsTr("col2")
formatDelegate: function(val) { return "!" + val}
}
]
Filling ListModel (id: columnModel):
Component.onCompleted: {
for(var i = 0; i < colDefines.length; ++i)
{
var col = colDefines[i];
...(some calculation)
columnModel.append(col);
}
}
All looks fine, but when I try to call format from model item, Qt sends me the following error
Property 'format' of object QQmlDMListAccessorData(0x8e3bf78) is not a function
Example of calling format:
Repeater {
model: columnModel
Text {
text: model.format([SOME USEFUL DATA])
}
}
On the other hand, if I call format directly from list it works well.
So my question here is how to fill model in a way that the format or other function will work correctly when being called from model?

Answer 1

For QtQuick2 this should work
formatDelegate = [function(val) { return "!" + val}]
formatDelegate[0]("some text")
but you could also use an overriding technique:
Item {
function formatDelegate(val) {
return val;
}
function format(val) {
return formatDelegate(val);
}
}
ColumnDescriptor {
function formatDelegate(val) {
return "!" + val
}
}
This way Item.format() should call "return val" as default and "!"+val for ColumnDescriptor given that ColumnDescriptor is derived from Item.

Answer 2

Try this
Repeater {
model: columnModel
Text {
text: columnModel[index].format([SOME USEFUL DATA])
}
}