源于群友的提问，以前项目中也遇到过的问题，最后在Qml帮助文档找到的解决方法。
下面代码中，Text对象绑定了car.wheels属性。当onCompleted执行完成时，car.wheels = 6也同样执行完成了。预想结果是Text对象会动态更新，但实际上是不会更新的。
Item {
property var car: new Object({wheels: 4})
Text {
text: "The car has " car.wheels " wheels";
}
Component.onCompleted: {
car.wheels = 6;
}
}
让我们看看Qml文档是如何描述的吧：
代码语言：javascript复制It is important to note that changes in regular properties of JavaScript objects assigned to a var property will not trigger updates of bindings that access them.
The example below will display "The car has 4 wheels" as the change to the wheels property will not cause the reevaluation of the binding assigned to the "text" property:
重要注意，
分配给var属性的JavaScript对象的常规属性中的更改不会触发访问它们的绑定的更新。
下面的示例将显示"The car has 4 wheels"，
因为车轮属性的更改不会导致重新求值分配给“文本”属性的绑定
那么我想更新Text对象呢，怎么更新呢？帮助文档同样也给出答案，就是更新整个car的属性：
If the onCompleted handler instead had "car = new Object({wheels: 6})" then the text would be updated to say "The car has 6 wheels",
since the car property itself would be changed, which causes a change notification to be emitted.
如果onCompleted处理程序具有 "car = new Object({wheels: 6})"，
则该文本将更新为"The car has 6 wheels"，
因为car属性本身将被更改，
这将导致更改通知被发射。
文档引用： https://doc.qt.io/qt-5/qml-var.html#change-notification-semantics
