通过属性在C ++和QML之间共享数组或列表

Question

There's a list of unsigned ints in C++ class. The list can be modified inside the class in some way. There's a QML object that has to use this list. How should I declare the list to make the object able to use the values from the list and after changing the content of the list inside C++ get appropriate values in QML?

Currently the list is defined as:

QVariantList cards; Q_PROPERTY(QVariantList cards MEMBER cards NOTIFY setChanged) void setChanged ( QVariantList const &cards );

But QML takes only cards initial value (empty list) and does not "notice" any changes inside it later on.

Answer 1

The need for NOTIFY signal is optional. I guess it is for when we need to deliberately let QML know that the data is ready but the data will be consumed when it READs data. Aside from this we can almost always avoid programming NOTIFY. I even do rootItem->setProperty("propertyName", value) for occasional push in of new value to QML especially if there onPropertyNameChanged handler is ready.

The below will likely do what you want. Or it is required and adding NOTIFY to that won't hurt as well but adds 'inoperability'.

class MyMsgBoard : public QObject
{
public:
    Q_PROPERTY(QVariantList cards READ cards WRITE setCards)
    const QVariantList & cards() const { return qvList; }
    void setCards(const QVariantList & v) { qvList = v; }
private:
    QVariantList qvList;
};

More detailed explanation . I use message board concept from there.