[Qt-interest] Qt MVC Questions

[Willy P]

Sean,
Thanks for writing back.  Late last night I came across the ProxyModel
classes.  I inherited from QSortFilterProxyModel and am attempting to
create mapTo / mapFrom source functions that, for starters, simply
pass the the values back and forth with no modification.  It is not
working at all:


	QModelIndex ReducedTreeModel::mapFromSource( const QModelIndex & source ) const
	{
		qDebug() << "from Source" << source.row() << source.column() <<
source.internalId();
		return createIndex( source.row(), source.column(), ( quint32
)source.internalId() );
	}



	QModelIndex ReducedTreeModel::mapToSource( const QModelIndex& proxy ) const
	{
		qDebug() << "to Source" << proxy.row() << proxy.column() <<
proxy.internalId();
		return (sourceModel()&&proxy.isValid())
				? sourceModel()->index(proxy.row(), proxy.column(), proxy.parent())
				: QModelIndex();
	}


Can you tell me what I'm doing wrong here?  It's crashing when an
absolutely junk value comes into mapToSource for proxy.internalId().

Thanks again...

-Willy



On Sun, Sep 20, 2009 at 4:21 AM, Sean Harmer
<sean.harmer at maps-technology.com> wrote:
> Willy P wrote:
>> I have built a Model, a view and a delegate that represents a tree
>> like data structure.
>>
>> Two related questions:
>>
>> 1)  Is there a way to hide TreeNodes in a view but show their
>> children?  Basically I have data structures that are programatically
>> useful but the user doesn't need to know about them.  So I'd like the
>> view to show the invisible node's children as if they were children of
>> the invisible node's parent.  I've tried setRowHidden() but it hides
>> all the children as well.
>>
> Try a custom class derived from QProxySortFilterModel.
>
>> 2)  The opposite question.  Is there a way to have nodes appear in the
>> view but not the model?  I basically want to add categorical
>> separators.  In some situations I want them and in others I don't, but
>> in no case do I need them in the raw model.
>>
> Once again a custom proxy that sits between your source model and your
> custom view(s) will be the way to go. I think that there is already some
> classes in KDE that do this. Yes, check out KCategorizedView and
> KCategorizedSortFilterProxyModel:
>
> http://api.kde.org/4.x-api/kdelibs-apidocs/kdeui/html/classKCategorizedView.html
> http://api.kde.org/4.x-api/kdelibs-apidocs/kdeui/html/classKCategorizedSortFilterProxyModel.html
>
> They should do what you need for (2) without any work needed on your part.
>
> Sean
>
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