过期属性已读

此警告类别由 qmllint 拼写[stale-property-read] 。

读取非常数和不可注属性

发生了什么？

绑定中使用了一个既非常数又不可通知的属性。

为什么会这样？

常量属性的值永远不会改变。可通知属性会在值发生变化时通知绑定，以便绑定可以重新评估。

由于该属性既不是常量属性，也不是可通知属性，因此它可能在程序执行过程中发生变化，而不会通知依赖的绑定。这将使绑定处于潜在的过时状态，因为它们的值取决于该属性。

示例

class Circle : public QObject
{
    Q_OBJECT
    QML_ELEMENT
    Q_PROPERTY(double radius READ radius WRITE setRadius FINAL)
public:
    double radius() const { return m_radius; }
    void setRadius(double radius) { m_radius = radius; }
private:
    double m_radius = 1;
};

import QtQuick

Item {
    Circle {
        id: circle
        property double area: Math.PI * radius * radius
    }

    Component.onCompleted: {
        console.log(circle.area) // 3.14159...
        circle.radius = 2
        console.log(circle.area) // 3.14159...
    }
}

要修复此警告，要么将不会改变值的属性标记为常量，要么将其设置为可通知属性。

class Circle : public QObject
{
    Q_OBJECT
    QML_ELEMENT
    Q_PROPERTY(double radius READ radius WRITE setRadius NOTIFY radiusChanged FINAL)
public:
    double radius() const { return m_radius; }
    void setRadius(double radius) {
        if (radius != m_radius) {
            m_radius = radius;
            emit radiusChanged();
        }
    }
signals:
    void radiusChanged();
private:
    double m_radius = 1;
};

import QtQuick

Item {
    Circle {
        id: circle
        property double area: Math.PI * radius * radius
    }

    Component.onCompleted: {
        console.log(circle.area) // 3.14159...
        circle.radius = 2
        console.log(circle.area) // 12.5663...
    }
}

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