QML属性绑定取决于同一组件中的其他绑定

Question

假设我有一个QtObject，它有一些属性。有没有用在其他在同一QtObject结合一个有约束力的任何缺点：

QtObject { 
    // This is set by the caller 
    property var myObject 

    readonly property bool haveMyObject: myObject ? true : false 
    readonly property bool isSomething1: haveMyObject ? myObject.isSomething1 : false 
    readonly property bool isSomething2: haveMyObject ? myObject.isSomething2 : false 
    readonly property bool isSomething3: haveMyObject ? myObject.isSomething3 : false 
    readonly property bool isSomething4: haveMyObject ? myObject.isSomething4 : false 
    readonly property bool isSomething5: haveMyObject ? myObject.isSomething5 : false 
} 

，而不是这样的：

QtObject { 
    // This is set by the caller 
    property var myObject 

    readonly property bool haveMyObject: myObject ? true : false 
    readonly property bool isSomething1: myObject ? myObject.isSomething1 : false 
    readonly property bool isSomething2: myObject ? myObject.isSomething2 : false 
    readonly property bool isSomething3: myObject ? myObject.isSomething3 : false 
    readonly property bool isSomething4: myObject ? myObject.isSomething4 : false 
    readonly property bool isSomething5: myObject ? myObject.isSomething5 : false 
} 

哪一个最好？我问的原因是因为Qt文档评估的顺序是不确定的。

Answer 1

订单完全未定义是不正确的。绑定以依赖关系定义的顺序进行评估。对于任何dependant-dependency对，保证在dependant之前评估dependency方。因此，每isSomething财产被评估/更新后它依赖haveMyObject已被评估/更新。