Use own Class in some Qt class

[Ichi]

Hi,
I start with example: i have for example QQuickView class and i want set my own instance of QQuickItem but how i know one way:
implement own instance of QQuickView class and use own QQuickItem class. This is hard way and only way or is there some another way to do this?

[wysota]

Please rephrase your question. It is hard to make out what you want.

[anda_skoa]

Indeed hard to understand the problem, but my guess is you are looking for qmlRegisterType()?

Cheers,
_

[Ichi]

ok i want use my own instance of QQuickItem in QQuickView. For example:
I make my class MyItem - public class Item : public QQuickItem
QQuickView *view = new QQuickView();
view->rootObject->itemsChild(); and i want that this will return QList<MyItem> items;

[wysota]

Do you mean that you want to be able to put instances of your MyItem class into QtQuick scene or that all items in the scene are MyItem instances instead of QQuickItem instances?

[Ichi]

all items in the scene are MyItem instances instead of QQuickItem instances

this is waht i want, sorry for hard understanding but i realy didn't know how say it

[wysota]

In that case that is not possible. Why do you want that?

[Ichi]

Because when i did one program i wanted to storage friend QQuickItem. I this case i have to use objectUserData method, but i think if i make own class it will much better but this is only one example this happen me few times

[wysota]

Because when i did one program i wanted to storage friend QQuickItem.

I don't understand what it means.

I this case i have to use objectUserData method

Why do you have to use that method (whatever it is)? And what does QQuickItem have to do with this?

[Ichi]

In this program every QquickItem has friends. And i need to get this friend. But i can't call function which get friends every time when i need it so it is comfortable when you can customise this class

[wysota]

In this program every QquickItem has friends.

What friends?

But i can't call function which get friends every time when i need it so it is comfortable when you can customise this class

I'm sorry, I don't understand you. I'm afraid I can't help.

[Ichi]

ok i think it doesn't matter what friend or whatever.
i simply wanted customise this class because in some cases it is much comfortable, i wanted add 2 or 3 methods this is all.

[d_stranz]

i simply wanted customise this class because in some cases it is much comfortable, i wanted add 2 or 3 methods this is all.

You can always derive a custom class from QQuickItem and add more methods to it.

However the QQuickItem::childItems() will always return QList< QQuickItem * >. You need to do something like this:

QList< QQuickItem * > children = root->childItems();
 
QListIterator< QQuickItem * > it( children );
while ( it.hasNext() )
{
   QQuickItem * pItem = it.next();
   MyItem * pMyItem = qobject_cast< MyItem * >( pItem );
   if ( pMyItem )  // check for NULL - if it is null, then the item was not a MyItem
   {
      pMyItem->callMyMethod();
   }
}

QList< QQuickItem * > children = root->childItems();

QListIterator< QQuickItem * > it( children );
while ( it.hasNext() )
{
   QQuickItem * pItem = it.next();
   MyItem * pMyItem = qobject_cast< MyItem * >( pItem );
   if ( pMyItem )  // check for NULL - if it is null, then the item was not a MyItem
   {
      pMyItem->callMyMethod();
   }
}

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[wysota]

qobject_cast will definitely fail here. He doesn't want to insert new items in the scene that are to be MyItem instances, he wants all items in the scene to magically be MyItem instances (because items in his scene have "friends") thus any cast other than a crude static_cast will fail. I don't understand the point of all this discussion, it seems to me OP just wants to do myItem->callMyMethod() instead of callMyMethod(myItem).

[anda_skoa]

Well, it is really unclear.

If the OP has a QtQuick item class and only creates those or subclasses of it, then the approach by d_stranz will of course work.

Ichi, can you provide a QML snippet showing your use of QtQuick?

Cjeers,
_

[d_stranz]

If the OP has a QtQuick item class and only creates those or subclasses of it, then the approach by d_stranz will of course work.

That's what I understood he was trying to say here:

ok i want use my own instance of QQuickItem in QQuickView. For example:
I make my class MyItem - public class Item : public QQuickItem
QQuickView *view = new QQuickView();
view->rootObject->itemsChild(); and i want that this will return QList<MyItem> items;

[wysota]

I don't see him create any instances of MyItem in here. And he also said he wants all items to be MyItem instances. I assumed there is no QtQuick program that can work without even a single instance of any predefined elements.

[anda_skoa]

I don't see him create any instances of MyItem in here.

I assumed that the whole scene is created in QtQuick. For QtQuick2 (which we have here judging by class name) this is basically the only sensible way.
Hence my request to see the QML part

And he also said he wants all items to be MyItem instances. I assumed there is no QtQuick program that can work without even a single instance of any predefined elements.

I don't see why it would not, i.e. I am not aware of any requirement to have a certain type for top level element, I assume it can be any QQuickItem subclass.

Cheers,
_

[Ichi]

simply forgot all what i said i want customise QQuickItem (add 2 methods). And use this for all items in QQuickView.

[d_stranz]

OK, then you will want to use something like the code I posted:

QList< QQuickItem * > children = root->childItems();
 
QListIterator< QQuickItem * > it( children );
while ( it.hasNext() )
{
    QQuickItem * pItem = it.next();
    MyItem * pMyItem = qobject_cast< MyItem * >( pItem );
    if ( pMyItem ) // check for NULL - if it is null, then the item was not a MyItem
    {
        pMyItem->callMyMethod();
    }
}

QList< QQuickItem * > children = root->childItems();
     
QListIterator< QQuickItem * > it( children );
while ( it.hasNext() )
{
    QQuickItem * pItem = it.next();
    MyItem * pMyItem = qobject_cast< MyItem * >( pItem );
    if ( pMyItem ) // check for NULL - if it is null, then the item was not a MyItem
    {
        pMyItem->callMyMethod();
    }
}

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