动态QML，编辑JS中实例的属性

Question

我正在使用JS创建对象的动态实例，并尝试在创建时设置属性。我先用宽度试了一下。

var component;
var gauge;

function createVerticalGauge() {
    component = Qt.createComponent("VerticalBarGauge.qml");
    if (component.status == Component.Ready)
        finishCreation();
    else
        component.statusChanged.connect(finishCreation);
}

function finishCreation() {
    if (component.status == Component.Ready) {
        gauge = component.createObject(root, {"x": 100, "y": 100});
        gauge.width = 300;
        if (gauge == null) {
            // Error Handling
            console.log("Error creating object");
        }
    } else if (component.status == Component.Error) {
        // Error Handling
        console.log("Error loading component:", component.errorString());
    }
}

但是javascript没有改变属性。编译时不会出现错误或警告。

这是由javascript：

创建的Object的QML

import QtQuick 2.8
import QtGraphicalEffects 1.0
import QtQuick.Controls 2.1
import QtQuick.Controls.Styles 1.4
import QtQuick.Extras 1.4


Item {

    Rectangle {
        id: rev
        width: 100
        height: 80
        color: "transparent"
        anchors.left: parent.left
        anchors.top: parent.top

        Gauge {
            id: revgauge
            anchors.fill: parent
            anchors.margins: 10
            orientation : Qt.Horizontal
            tickmarkStepSize : 5000
            minimumValue: 0
            maximumValue: 10000

            //value: Dashboard.revs
            Behavior on value {
                NumberAnimation {
                    duration: 5
                }
            }
            Text {
                font.pixelSize: (parent.height / 3)
                anchors.top : parent.top
                font.bold: true
                font.family: "Eurostile"
                color: "white"
                anchors.horizontalCenter: parent.horizontalCenter
            }
              style: GaugeStyle {
                valueBar: Rectangle {
                   implicitWidth:  rev.height /3
                    color: Qt.rgba(revgauge.value / revgauge.maximumValue, 0, 1 - revgauge.value / revgauge.maximumValue, 1)
                }
            }
      }
    }
}

如何在创建对象后更改对象的属性。例如。我想改变对象的位置或颜色。