qml property twoway sync.

twoway.qml

import QtQuick 2.0
import QtQuick.Controls 1.0


Column {
    CheckBox {
        id:a1
        text:"A1"
        Binding { target :a2; property: "checked"; value:a1.checked }
    }
    CheckBox {
        id:a2
        Binding { target :a1; property: "checked"; value:a2.checked }
        text:"A2"
    }
    Text {
        text:"A1:" + a1.checked + "  A2:" + a2.checked + "---------------------------"
    }


    //this is failed sync
    CheckBox {
        id:b1
        text : "B1"
        checked: b2.checked
    }
    CheckBox {
        id:b2
        text : "B2"
        checked: b1.checked
    }
}