Column {
        Repeater {
            model: 3
            ComboBoxListItem {
                itemText: "this is the " + index + " string"
            }
        }
    }

function setRandomText() 
{
    for (var i = 0; i < textItemStack.children.length; ++i) 
    {
        textItemStack.children[i].text = Math.random("fff")
    }
}

Item {
    id: textItemStack
...    
    onFocusChanged: setRandomText()
}

Item {
    id: textItemStack
...    
    setRandomText()
}