Hi Mark, How would one use QCollatorSortKey for this type of application?
Unfortunately I have to say that the Qt documentation on this class is not as descriptive compared to other classes. Regards, Carel On Mon, Jan 8, 2018 at 11:50 AM, Mark Gaiser <[email protected]> wrote: > On Mon, Jan 8, 2018 at 4:18 AM, jack ma <[email protected]> wrote: > >> Thanks all of you, seems that std::sort + QCollator is a good way >> >> 2018-01-07 18:47 GMT+08:00 Konstantin Tokarev <[email protected]>: >> >>> >>> >>> > Hi, >>> > >>> > you need a "lessThan"-function, tailored for your needs. An >>> > example from me is this: >>> > >>> > bool Person::lessThanFamilyFirst(QSharedPointer<Person> >>> > p1, QSharedPointer<Person> >>> > p2) >>> > >>> > { >>> > >>> > return (QString::localeAwareCompare(p1->familyName(),p2->familyName >>> ())<0) >>> > >>> > || (( p1->familyName() == p2->familyName()) >>> > >>> > && (QString::localeAwareCompare(p1->firstName(),p2->firstName())<0)); >>> > >>> > } >>> > >>> > Now you can pass this as a functor to a sort method like this: >>> > >>> > std::stable_sort(pupils.begin(), pupils.end(), >>> Person::lessThanFamilyFirst); >>> >>> FWIW, if this is not a list displayed in UI, or other place where >>> preserving order of >>> equal elements matters, you should consider std::sort >>> >>> > >>> > Please notice, that there are no () when calling the lessThan functor. >>> >>> Original question was dealing with QMap. While sorted vector-like >>> container can replace >>> map (there is even convenience wrapper flat_map in Boost, which allows >>> to work with >>> sorted array just like it was a "true" map), it doesn't always fit, e.g. >>> inserts in such >>> "flat map" are very expensive. >>> >>> So, you can just replace QMap with std::map and pass your comparator, >>> e.g. >>> >>> auto comparator = [](const QString &a, const QString &b) -> bool { >>> // Your comparison function here >>> }; >>> std::map<QString, QGraphicsItem *, decltype(comparator)> >>> myMap(comparator); >>> >>> See [1] for more examples. >>> >>> Yet another approach is to use your own type as a key of QMap instead of >>> QString, >>> and create desired operator< for it. This has a downside that your >>> access to internal >>> QString will be more complicated, and you'll have to invent different >>> key type each time >>> you want to change comparator. >>> >>> And, last but not least: you probably want to know *how* to write >>> comparator for your >>> particular sorting order. You can do this with QCollator, see [2]. >>> >>> [1] http://en.cppreference.com/w/cpp/container/map/map >>> [2] https://forum.qt.io/topic/68910/natural-sort-using-qcollator/2 >>> >>> > >>> > HTH >>> > Sebastian >>> > >>> > Am 07.01.2018 um 09:01 schrieb jack ma: >>> > >>> >> Hi, >>> >> >>> >> there is a QMap<QString,QGraphicsItem *> type, then >>> >> insert values with： >>> >> >>> >> type.insert("U1",nullptr), >>> >> >>> >> type.insert("U2",nullptr), >>> >> >>> >> ………… >>> >> >>> >> type.insert("U9",nullptr), >>> >> >>> >> type.insert("U10",nullptr), >>> >> >>> >> I want get the values follow the order of U1, U2 ... U10， >>> >> but the default order is U1, U10 ,……U9 >>> >> >>> >> I know this is a common string sorting problem, but I do >>> >> not know how to solve it well. >>> >> >>> >> Any suggestions are very grateful ! >>> >> >>> >> Thanks. >>> >> >>> >> _______________________________________________ >>> >> Interest mailing list >>> >> [email protected] >>> >> http://lists.qt-project.org/mailman/listinfo/interest >>> > >>> > -- >>> > http://www.classintouch.de - Tablet-Software für Lehrer >>> -- >>> Regards, >>> Konstantin >>> _______________________________________________ >>> Interest mailing list >>> [email protected] >>> http://lists.qt-project.org/mailman/listinfo/interest >>> >> >> >> _______________________________________________ >> Interest mailing list >> [email protected] >> http://lists.qt-project.org/mailman/listinfo/interest >> >> > Hi, > > You might want to look into std::map[1] as well. It allows setting a > compare function, QMap doesn't. > Going that route is most likely more efficient as your inserts will be > sorted, no need to do std::sort afterwards. > > You still would have to use QCollator. Note that you can just use > QCollator in the compare method which will work just fine, but is not the > performant way to go. > The most performant way (i know of) is by using QCollatorSortKey[2]. > > > [1] http://en.cppreference.com/w/cpp/container/map/map > [2] http://doc.qt.io/qt-5/qcollatorsortkey.html > > _______________________________________________ > Interest mailing list > [email protected] > http://lists.qt-project.org/mailman/listinfo/interest > >
_______________________________________________ Interest mailing list [email protected] http://lists.qt-project.org/mailman/listinfo/interest
