On 22/08/12 00:54, Stephen Chu wrote: > On 8/21/12 5:47 PM, Nikos Chantziaras wrote: >> On 21/08/12 23:55, Stephen Chu wrote: >>> On 8/21/12 4:26 PM, Nikos Chantziaras wrote: >>>> On 21/08/12 22:45, Stephen Chu wrote: >>>>> On 8/21/12 3:35 PM, Christoph Feck wrote: >>>>>> On Tuesday 21 August 2012 20:55:00 Stephen Chu wrote: >>>>>>> Is there a way to store a 64-bit internal ID in QModelIndex? The >>>>>>> function QModelIndex::internalId() returns a 64-bit number but >>>>>>> there's no way to put one in. The constructor takes only a 32-bit >>>>>>> integer. >>>>>> >>>>>> Try using the overload that takes the void * pointer. The return value >>>>>> is 64 bit, because pointers can also be 64 bit, and C++ doesn't allow >>>>>> different overloads with different return values. >>>>> >>>>> Thanks for the help. But my app is currently 32-bit. :( >>>> >>>> Would a pointer to a qint64 work? >>> >>> Yes, it will. I was thinking about that but got stuck trying to figuring >>> out how I can manage the memory since QModelIndedx does not own the >>> object/memory pointed by the void* >>> >>> Say I allocate a QList<int64_t> and create indices with internal pointer >>> pointing to elements in the list. When I need to update the model from >>> external data, I will have to re-allocate the list and the existing >>> pointers will be left dangling. What is the proper steps to update the >>> model data in this case? >> >> Note that I didn't work with QAbstractItemModel before, so perhaps I'm >> not the most suitable person here to give advice. With that being said, >> you might be able to allocate like this: >> >> createIndex(row, column, new qint64(value)); >> >> Access the value with: >> >> *(qint64*)internalPointer(); >> >> And when you don't need the QModelIndex anymore, you deallocate like this: >> >> delete (qint64*)internalPointer(); >> >> You should probably create wrappers for those operations. Or work out a >> subclass model. >> >> But again, I didn't work with that part of Qt before, so I might be >> talking gibberish here ;-) >> > > Actually it makes a lot of sense and I was trying to do the same. But I > can not find out when a QModelIndex is no longer in use.
I see QAbstractItemModel has some signals: columnsAboutToBeRemoved() rowsAboutToBeRemoved() It also has some virtual functions: removeRows() removeColumns() They might be of some help in determining what's no longer needed. _______________________________________________ Interest mailing list Interest@qt-project.org http://lists.qt-project.org/mailman/listinfo/interest
