Properties undefined when accessed through script



  • I'm encountering a problem that I've been trying to solve for a while: http://stackoverflow.com/questions/16310311/properties-undefined-only-when-accessed-through-script

    A property can be accessed directly through QObject's property function, but not through JS:

    @#include <QApplication>
    #include <QDebug>
    #include <QScriptEngine>
    #include <QStringList>

    class Item : public QObject
    {
    Q_OBJECT
    public:
    Q_PROPERTY(int typeId READ typeId)
    Q_PROPERTY(int usesLeft READ usesLeft)

    Item() :
        mTypeId(0),
        mUsesLeft(-1)
    {
    }
    
    Item(int typeId) :
        mTypeId(typeId)
    {
        if (typeId != 0) {
            mUsesLeft = 5;
        }
    }
    
    Item(const Item &item) :
        QObject(0)
    {
        *this = item;
    }
    
    ~Item()
    {
    }
    
    Item& operator=(const Item& rhs)
    {
        mTypeId = rhs.mTypeId;
        mUsesLeft = rhs.mUsesLeft;
        return *this;
    }
    
    int typeId() const { return mTypeId; }
    
    int usesLeft() const { return mUsesLeft; }
    void setUsesLeft(int usesLeft) { mUsesLeft = usesLeft; }
    
    friend QDataStream &operator<<(QDataStream &out, const Item &item);
    friend QDataStream &operator>>(QDataStream &in, Item &item);
    friend QDebug operator<<(QDebug debug, const Item &item);
    

    private:
    int mTypeId;
    int mUsesLeft;
    };

    QDataStream &operator<<(QDataStream &out, const Item &item)
    {
    out << item.typeId()
    << item.usesLeft();
    return out;
    }

    QDataStream &operator>>(QDataStream &in, Item &item)
    {
    in >> item.mTypeId
    >> item.mUsesLeft;
    return in;
    }

    QDebug operator<<(QDebug debug, const Item &item)
    {
    debug.nospace() << "(Item typeId=" << item.typeId()
    << ", usesLeft=" << item.usesLeft();
    return debug.space();
    }

    Q_DECLARE_METATYPE(Item)

    class ItemStack : public QObject
    {
    Q_OBJECT
    public:
    Q_PROPERTY(Item *item READ item)
    Q_PROPERTY(int size READ size)

    ItemStack() :
        mSize(0)
    {
    }
    
    ItemStack(const ItemStack &rhs) :
        QObject()
    {
        *this = rhs;
    }
    
    ItemStack(const Item &item, int size) :
        mItem(item),
        mSize(size)
    {
    }
    
    ~ItemStack()
    {
    }
    
    ItemStack& operator=(const ItemStack& rhs)
    {
        if(this == &rhs) return *this;
    
        mItem = rhs.mItem;
        mSize = rhs.mSize;
    
        return *this;
    }
    
    Item* item()
    {
        return &mItem;
    }
    
    const Item *item() const
    {
        return &mItem;
    }
    
    int size() const
    {
        return mSize;
    }
    
    friend QDataStream &operator&lt;&lt;(QDataStream &out, const ItemStack &itemStack);
    friend QDataStream &operator&gt;&gt;(QDataStream &in, ItemStack &itemStack);
    friend QDebug operator&lt;&lt;(QDebug debug, const ItemStack &itemStack);
    

    private:
    Item mItem;
    int mSize;
    };

    QDataStream &operator<<(QDataStream &out, const ItemStack &itemStack)
    {
    out << *itemStack.item()
    << itemStack.size();
    return out;
    }

    QDataStream &operator>>(QDataStream &in, ItemStack &itemStack)
    {
    in >> itemStack.mItem
    >> itemStack.mSize;
    return in;
    }

    QDebug operator<<(QDebug debug, const ItemStack &itemStack)
    {
    debug.nospace() << "(ItemStack item=" << *itemStack.item()
    << ", size=" << itemStack.size()
    << ")";
    return debug.space();
    }

    Q_DECLARE_METATYPE(ItemStack)

    class GunEntity : public QObject
    {
    Q_OBJECT
    public:
    Q_PROPERTY(ItemStack roundsLoaded READ roundsLoaded)

    GunEntity() : mRoundsLoaded(Item(1), 7) {}
    
    ItemStack roundsLoaded() { return mRoundsLoaded; }
    

    private:
    ItemStack mRoundsLoaded;
    };

    int main(int argc, char *argv[])
    {
    QApplication a(argc, argv);

    // Accessing directly through properties.
    GunEntity ge;
    qDebug() << "Can convert ge.roundsLoaded to ItemStack?" << ge.property("roundsLoaded").canConvert<ItemStack>();
    ItemStack is = ge.property("roundsLoaded").value<ItemStack>();
    qDebug() << is;
    qDebug() << "Can convert is.item to Item?" << is.property("item").canConvert<Item*>();
    qDebug() << *is.property("item").value<Item*>();
    qDebug() << "Can convert is.size to int?" << is.property("size").canConvert<int>();
    qDebug() << is.property("size").toInt();
    
    // Accessing through QScriptEngine.
    QScriptEngine se;
    se.evaluate("function blah(gun) { print(gun.roundsLoaded); print(gun.roundsLoaded.item); print(gun.roundsLoaded.size); }");
    if (se.hasUncaughtException()) {
        qDebug() << se.uncaughtException().toString() << ":"
                 << se.uncaughtExceptionLineNumber() << se.uncaughtExceptionBacktrace();
    }
    QScriptValueList args;
    args << se.newQObject(&ge);
    QScriptValue ret = se.globalObject().property("blah").call(se.globalObject(), args);
    
    if (se.hasUncaughtException()) {
        qDebug() << se.uncaughtException().toString() << ":"
                 << se.uncaughtExceptionLineNumber() << se.uncaughtExceptionBacktrace();
    }
    
    return 0;
    

    }

    #include "main.moc"@

    Any suggestions are welcomed. :)


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