[Interest] Pointers as Q_PPOPERTY

[Николай Шатохин]

Can I use QList (or something similar) as Q_PROPERTY? How can I use it in
QML? Can I use QList of pointers? And get objects in QML

Best regards,
Nick


2013/10/4 Николай Шатохин <n.shatokhin at gmail.com>

> Yes, I did exactly the same. Thanks.
>
>
> 2013/10/4 Bo Thorsen <bthorsen at ics.com>
>
>> 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
>>
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.qt-project.org/pipermail/interest/attachments/20131007/4a99106c/attachment.html>