在C++中声明一个可供Qml读写的属性

原型：

class ClassName : public QObject
{
    Q_OBJECT
    QString m_test;

    Q_PROPERTY(QString test READ test WRITE setTest NOTIFY testChanged)

signals:
    void testChanged(QString arg);

public slots:
    void setTest(QString arg)
    {
        if (m_test != arg) {
            m_test = arg;
            emit testChanged(arg);
        }
    }

public:
    QString test() const
    {
        return m_test;
    }

}

为了代码简洁，可先定义一个Qml属性导出宏：

#define QML_PROPERTY(type, name, \
    READ, getter, \
    WRITE, setter, \
    NOTIFY, notifyer\
    )  \
    type m_##name; \
    Q_PROPERTY(type name READ getter WRITE setter NOTIFY notifyer) \
    public: type getter##() const { return m_##name; } \
    public Q_SLOTS: void setter##(type arg) { if (m_##name != arg) {m_##name = arg; emit notifyer##(arg);}} \
    Q_SIGNALS:  \
        void notifyer##(type arg); \
    private:

则以上类可如下定义：

class ClassName : public QObject
{
    Q_OBJECT

   QML_PROPERTY(QString, test, READ, test, WRITE, setTest, NOTIFY, testChanged)
}

如此无论是通过类注册还是实例上下文，可在Qml中可以访问该属性，并可以调用其方法。