Qt-interest Archive, April 2008
QMap<QPersistentModelIndex, ...> searching problem
Message 1 in thread
Hi !
I have a problem finding values in a QMap:
I have a QMap with the following type:
QMap<QPersistentModelIndex, QGraphicsItem*>
Everything works fine until I do a changePersistentIndexList () in my
QAbstractItemModel from which the QPersistentModelIndex used as keys
in my QMap are issued.
Then sometimes:
my_qmap.find (some_model_index) == my_qmap.end ()
return true although some_model_index is in the QMap.
So when this happen, I do the following:
std::map<QPersistentModelIndex, QGraphicsItem*> test = my_qmap.toStdMap ();
and
test.find (some_model_index) == test.end ()
return false, meaning some_model_index is found.
I also try finding the some_model_index index manually, by doing:
foreach (QPersistentModelIndex p, my_qmap.keys ())
if (p == some_model_index)
qDebug () << "Hurray !"
<< (p == some_model_index)
<< (p < some_model_index)
<< (some_model_index < p);
and I get "Hurray ! true false false" displayed.
My question is: what is this behaviour ? Why isn't the index found by the QMap
find () method while I can find it manually or in a std::map ?
If someone has any clue I would appreciate.
--
[ signature omitted ]
Message 2 in thread
Looks like a bug. Make a small compilable example that shows the problem?
Cheers,
Peter
> -----Ursprüngliche Nachricht-----
> Von: remi humbert [mailto:remi.humbert@xxxxxxxxx]
> Gesendet: Mittwoch, 2. April 2008 13:32
> An: qt-interest@xxxxxxxxxxxxx
> Betreff: QMap<QPersistentModelIndex, ...> searching problem
>
> Hi !
>
> I have a problem finding values in a QMap:
>
> I have a QMap with the following type:
>
> QMap<QPersistentModelIndex, QGraphicsItem*>
>
> Everything works fine until I do a changePersistentIndexList () in my
> QAbstractItemModel from which the QPersistentModelIndex used as keys
> in my QMap are issued.
>
> Then sometimes:
>
> my_qmap.find (some_model_index) == my_qmap.end ()
>
> return true although some_model_index is in the QMap.
>
> So when this happen, I do the following:
>
> std::map<QPersistentModelIndex, QGraphicsItem*> test =
> my_qmap.toStdMap ();
>
> and
>
> test.find (some_model_index) == test.end ()
>
> return false, meaning some_model_index is found.
>
> I also try finding the some_model_index index manually, by doing:
>
> foreach (QPersistentModelIndex p, my_qmap.keys ())
> if (p == some_model_index)
> qDebug () << "Hurray !"
> << (p == some_model_index)
> << (p < some_model_index)
> << (some_model_index < p);
>
> and I get "Hurray ! true false false" displayed.
>
> My question is: what is this behaviour ? Why isn't the index
> found by the QMap
> find () method while I can find it manually or in a std::map ?
> If someone has any clue I would appreciate.
>
> --
> Humbert Remi
>
> --
> To unsubscribe - send a mail to
> qt-interest-request@xxxxxxxxxxxxx with "unsubscribe" in the
> subject or the body.
> List archive and information: http://lists.trolltech.com/qt-interest/
>
>
--
[ signature omitted ]
Message 3 in thread
Ok the problem was:
QMap (or QHash, I have also tried with a QHash instead of QMap and got
the same problem)
sort it's keys.
I use QPersistentModelIndex as keys. When I sort my model, I do
changePersistentIndexList () which
reorder the QPersistentModelIndexes. But QMap is unaware of that and
start having a wrong behaviour.
(it cant find the keys that have been swapped)
The only solution I found is to recreate a temporary map tmp_map from
my_qmap, then do
my_qmap.clear ();
my_qmap = tmp_map;
On Wed, Apr 2, 2008 at 1:49 PM, Peter Prade <prade@xxxxxxxxxxx> wrote:
> Looks like a bug. Make a small compilable example that shows the problem?
>
> Cheers,
> Peter
>
> > -----Ursprüngliche Nachricht-----
> > Von: remi humbert [mailto:remi.humbert@xxxxxxxxx]
> > Gesendet: Mittwoch, 2. April 2008 13:32
> > An: qt-interest@xxxxxxxxxxxxx
> > Betreff: QMap<QPersistentModelIndex, ...> searching problem
>
>
> >
> > Hi !
> >
> > I have a problem finding values in a QMap:
> >
> > I have a QMap with the following type:
> >
> > QMap<QPersistentModelIndex, QGraphicsItem*>
> >
> > Everything works fine until I do a changePersistentIndexList () in my
> > QAbstractItemModel from which the QPersistentModelIndex used as keys
> > in my QMap are issued.
> >
> > Then sometimes:
> >
> > my_qmap.find (some_model_index) == my_qmap.end ()
> >
> > return true although some_model_index is in the QMap.
> >
> > So when this happen, I do the following:
> >
> > std::map<QPersistentModelIndex, QGraphicsItem*> test =
> > my_qmap.toStdMap ();
> >
> > and
> >
> > test.find (some_model_index) == test.end ()
> >
> > return false, meaning some_model_index is found.
> >
> > I also try finding the some_model_index index manually, by doing:
> >
> > foreach (QPersistentModelIndex p, my_qmap.keys ())
> > if (p == some_model_index)
> > qDebug () << "Hurray !"
> > << (p == some_model_index)
> > << (p < some_model_index)
> > << (some_model_index < p);
> >
> > and I get "Hurray ! true false false" displayed.
> >
> > My question is: what is this behaviour ? Why isn't the index
> > found by the QMap
> > find () method while I can find it manually or in a std::map ?
> > If someone has any clue I would appreciate.
> >
> > --
> > Humbert Remi
> >
> > --
> > To unsubscribe - send a mail to
> > qt-interest-request@xxxxxxxxxxxxx with "unsubscribe" in the
> > subject or the body.
> > List archive and information: http://lists.trolltech.com/qt-interest/
> >
> >
>
> --
> To unsubscribe - send a mail to qt-interest-request@xxxxxxxxxxxxx with "unsubscribe" in the subject or the body.
> List archive and information: http://lists.trolltech.com/qt-interest/
>
>
--
[ signature omitted ]
Message 4 in thread
I see, you're changing the order of the keys, but QMap can't handle this.
Maybe you could use a QHash (which isn't ordered) instead, this should work, if you can come up with a qHash() implementation that doesn't result in different hash values when you call changePersistentIndexList().
Cheers,
Peter
> -----Ursprüngliche Nachricht-----
> Von: remi humbert [mailto:remi.humbert@xxxxxxxxx]
> Gesendet: Mittwoch, 2. April 2008 15:47
> An: Peter Prade
> Cc: qt-interest@xxxxxxxxxxxxx
> Betreff: Re: QMap<QPersistentModelIndex, ...> searching problem
>
> Ok the problem was:
>
> QMap (or QHash, I have also tried with a QHash instead of QMap and got
> the same problem)
> sort it's keys.
>
> I use QPersistentModelIndex as keys. When I sort my model, I do
> changePersistentIndexList () which
> reorder the QPersistentModelIndexes. But QMap is unaware of that and
> start having a wrong behaviour.
> (it cant find the keys that have been swapped)
>
> The only solution I found is to recreate a temporary map tmp_map from
> my_qmap, then do
> my_qmap.clear ();
> my_qmap = tmp_map;
>
>
> On Wed, Apr 2, 2008 at 1:49 PM, Peter Prade <prade@xxxxxxxxxxx> wrote:
> > Looks like a bug. Make a small compilable example that
> shows the problem?
> >
> > Cheers,
> > Peter
> >
> > > -----Ursprüngliche Nachricht-----
> > > Von: remi humbert [mailto:remi.humbert@xxxxxxxxx]
> > > Gesendet: Mittwoch, 2. April 2008 13:32
> > > An: qt-interest@xxxxxxxxxxxxx
> > > Betreff: QMap<QPersistentModelIndex, ...> searching problem
> >
> >
> > >
> > > Hi !
> > >
> > > I have a problem finding values in a QMap:
> > >
> > > I have a QMap with the following type:
> > >
> > > QMap<QPersistentModelIndex, QGraphicsItem*>
> > >
> > > Everything works fine until I do a
> changePersistentIndexList () in my
> > > QAbstractItemModel from which the QPersistentModelIndex
> used as keys
> > > in my QMap are issued.
> > >
> > > Then sometimes:
> > >
> > > my_qmap.find (some_model_index) == my_qmap.end ()
> > >
> > > return true although some_model_index is in the QMap.
> > >
> > > So when this happen, I do the following:
> > >
> > > std::map<QPersistentModelIndex, QGraphicsItem*> test =
> > > my_qmap.toStdMap ();
> > >
> > > and
> > >
> > > test.find (some_model_index) == test.end ()
> > >
> > > return false, meaning some_model_index is found.
> > >
> > > I also try finding the some_model_index index manually, by doing:
> > >
> > > foreach (QPersistentModelIndex p, my_qmap.keys ())
> > > if (p == some_model_index)
> > > qDebug () << "Hurray !"
> > > << (p == some_model_index)
> > > << (p < some_model_index)
> > > << (some_model_index < p);
> > >
> > > and I get "Hurray ! true false false" displayed.
> > >
> > > My question is: what is this behaviour ? Why isn't the index
> > > found by the QMap
> > > find () method while I can find it manually or in a std::map ?
> > > If someone has any clue I would appreciate.
> > >
> > > --
> > > Humbert Remi
--
[ signature omitted ]
