Loader doesn't immediately destroy the loaded item, and hence cannot be used to ensure a loaded item can freely reference properties that are only valid while the item is loaded

import QtQuick 2.4
import QtQuick.Window 2.2
import QtQuick.Controls 1.0

Window {
    id: window
    visible: true

    Item {
        id: theGame

        property bool isReady: false

        onStateChanged: {
            if (state == "invalid") {
                print("game.isReady about to change to false...")
                isReady = false;
                print("... game.isReady changed to " + isReady + "; nothing should reference properties of game now")

                player.destroy();
                player = null;
            } else if (state == "running") {
                player = Qt.createQmlObject("import QtQuick 2.0; Item { property color color: 'black' }", window);

                print("game.isReady about to change to true...")
                isReady = true;
                print("... game.isReady changed to true")
            }
        }

        property Item player
    }

    Column {
        Button {
            text: "Load Game"
            onClicked: {
                theGame.state = "running";
            }
        }

        Button {
            text: "Quit Game"
            onClicked: {
                theGame.state = "invalid";
            }
        }
        Loader {
            active: theGame.isReady
            Component.onCompleted: setSource("qrc:/LoaderItem.qml", { "game": theGame })
        }
    }
}

import QtQuick 2.0

Rectangle {
    width: 400
    height: 400
    color: game.player.color

    property var game
}

color: game.isReady ? game.player.color : "transparent"