Hi Николай Шатохин,
I saw on the list, that you got this working. But there were a bunch of
things missing in the discussion. I have just done the same thing you
are trying in one of our 4.8.5 based projects.
Some of this has been said, other parts haven't. I hope this is a
complete description that should help you understand the topic.
Den 02-10-2013 16:12, Николай Шатохин skrev:
> I registered as QML Type class Ship inherited from QObject that have fields:
>
> Q_PROPERTY(Hull hull READ hull)
> Q_PROPERTY(Reactor reactor READ reactor)
> Q_PROPERTY(Shields shields READ shields)
>
> (all field classes inherited from QObject too)
>
> But in ship class I'm using this fields as pointers (Hull * hull). So,
> how to use correctly Q_Properties in this case? (I need call methods
> from this fields and catch signals from them in QML)
>
> Can I use something like this Q_PROPERTY(Hull hull READ hull)?
As already pointed out, you have to do pointers for this:
class Hull : public QObject { ... };
class Ship : public QObject {
Q_OBJECT
Q_PROPERTY(Hull* hull READ hull CONSTANT)
Hull* m_hull;
public:
Ship() : m_hull(new Hull(this)) {}
Hull* hull() { return m_hull; }
};
The Reactor and Shields work exactly the same way.
For this to work, you have to declare the Hull, Reactor and Shields
types to the QML engine. Something like this:
qmlRegisterUncreatableType<Hull>("MyGame", 1, 0, "Hull", "Can't be
created.");
qmlRegisterType<Ship>("MyGame", 1, 0, "Ship");
> And then in QML:
>
> Ship
> {
> id: ship
> Hull
> {
> id: hull_indicator
> backend: ship.hull
> }
>
> onDamage:
> {
> ship.hull.reduce(damage);
> }
> }
You don't need the extra Hull {} declaration here. There is already a
Hull object in your ship, the "ship.hull" you use in onDamage.
If this is about visualization, you should have a different set of
classes, ShipView and HullView or something, that shows this:
import MyGame 1.0
Item {
id: completeShip
ShipView {
anchors.fill: parent
ship: internal.ship
}
HullView {
anchors.fill: parent
hull: internal.ship.hull
}
QtObject {
id: internal
Ship {
id: ship
}
}
}
This might seem complicated at first, but you achieve one thing I find
extremely important in QML coding: Keep your state in C++ and totally
separated from the visualization of it.
This is a standard MVC pattern, actually. The Ship is the model, the
completeShip is the controller and ShipView/HullView is the
visualization. But somehow this isn't always followed when people code QML.
I hope this helps.
Bo.
--
Bo Thorsen, European Qt Manager, ICS
Integrated Computer Solutions. Delivering World-Class Applications
http://ics.com/services
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