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[SOLVED] QPersistentModelIndex usage

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  • raven-worxR Offline
    raven-worxR Offline
    raven-worx
    Moderators
    wrote on last edited by
    #2

    just pass your QModelIndex to the constructor of QPersistentModelIndex and your good to go.

    You then can save the QPersistentModelIndex. And don't forget to check for validity of the persistent index every time you use it.

    --- SUPPORT REQUESTS VIA CHAT WILL BE IGNORED ---
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    • K Offline
      K Offline
      Kobid
      wrote on last edited by
      #3

      Yes but I don't know how to create QModelIndex for current changed item. For example, lets say that I have this tree:

      @-A (0,0)
      |-D (0,0)
      |-E (1,0)
      -B (1,0)
      -C (2,0)@

      Now I want to add new item between D and E.

      1. I know that the parent HCDirItem is A
      2. I'm creating new instance F of HCDirItem and appending it to the parent by calling A.appendChild(F)
      3. Now I need to create QModelIndex for QPersistentModelIndex. index() function need 3 arguments, I know which row (1) and column (0) it is. But third arguments is parent QModelIndex and I don't know what to set here
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      • raven-worxR Offline
        raven-worxR Offline
        raven-worx
        Moderators
        wrote on last edited by
        #4

        the parent is the QModelIndex of A.
        And if it's a top level item, then the parent is a invalid QModelIndex()

        --- SUPPORT REQUESTS VIA CHAT WILL BE IGNORED ---
        If you have a question please use the forum so others can benefit from the solution in the future

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        • K Offline
          K Offline
          Kobid
          wrote on last edited by
          #5

          I still don't understand :P . Ok more complicated example:

          @A
          |- B
          |- C
          |- D@

          Now if I want to create QModelIndex for D as third example I need QModelindex of C but to create index for C I need parent of C which is B etc. I need enumerate all parents to get index for D?

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          • raven-worxR Offline
            raven-worxR Offline
            raven-worx
            Moderators
            wrote on last edited by
            #6

            yes ... or you use the parent() of a already known index

            --- SUPPORT REQUESTS VIA CHAT WILL BE IGNORED ---
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            • K Offline
              K Offline
              Kobid
              wrote on last edited by
              #7

              So can I just create public QModelIndex index variable in HCDirItem object and setup it when item is created? Because I don't see difference between QModelIndex and QPersistentModelIndex

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              • raven-worxR Offline
                raven-worxR Offline
                raven-worx
                Moderators
                wrote on last edited by
                #8

                the difference is that the QPersistentIndex gets automatically invalid when the QModelIndex gets invalid (when they do not point to valid data anymore in the model). QModelIndexes don't.
                Think of it like QPointer for ordinary pointers.

                --- SUPPORT REQUESTS VIA CHAT WILL BE IGNORED ---
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                • K Offline
                  K Offline
                  Kobid
                  wrote on last edited by
                  #9

                  Thanks! Now it is working perfect! I'm just wondering how it is working. For example. Each item is holding QPersistentModelIndex of its self. Now if I have this list:

                  aaaa
                  bbbb
                  cccc

                  QList is holding these items. Now when I add new item

                  aaaa
                  bbbb
                  cccc
                  abc

                  ... it has QPersistentModelIndex (3,0). Same for QModelIndex. If I sort QList using qSort then list looks like:

                  aaaa
                  abc
                  bbbb
                  cccc

                  abc still has QPersistentModelIndex (3,0) but QTreeView.currentIndex is (1,0).

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                  • K Offline
                    K Offline
                    Kobid
                    wrote on last edited by
                    #10

                    Last question. Can I use QPersistenModelIndex to build normal index? For example: I know that data in known QPersistenModelIndex changed. I need to emit dataChanged. My QPersistenModelIndex always point to first (0) column but I want to update whole row, so I need to create second index as "to" and point to the last column. Can I use QPersistenModelIndex.row() for "to" in QModelIndex? I'm confused because QPersistenModelIndex.row() point to old row after sorting.

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                    • raven-worxR Offline
                      raven-worxR Offline
                      raven-worx
                      Moderators
                      wrote on last edited by
                      #11

                      how do you sort? Using a QSortFilterProxyModel? Or in a custom model?

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                      • K Offline
                        K Offline
                        Kobid
                        wrote on last edited by
                        #12

                        No, I'm using qSort on QList<HCFileItem>

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                        • raven-worxR Offline
                          raven-worxR Offline
                          raven-worx
                          Moderators
                          wrote on last edited by
                          #13

                          and are you sure you are triggering the right signals of the model to inform about the model change?

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                          • K Offline
                            K Offline
                            Kobid
                            wrote on last edited by
                            #14

                            I think so:

                            @emit layoutAboutToBeChanged();
                            qSort(childItems.begin(), childItems.end(), compareFilenameA);
                            emit layoutChanged();@

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                            • raven-worxR Offline
                              raven-worxR Offline
                              raven-worx
                              Moderators
                              wrote on last edited by
                              #15

                              try "QAbstractItemModel::dataChanged()":http://qt-project.org/doc/qt-4.8/qabstractitemmodel.html#dataChanged
                              If it doesn't make a difference you can also try "QAbstractItemModel::changePersistentIndex()":http://qt-project.org/doc/qt-4.8/qabstractitemmodel.html#changePersistentIndex

                              --- SUPPORT REQUESTS VIA CHAT WILL BE IGNORED ---
                              If you have a question please use the forum so others can benefit from the solution in the future

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                              • K Offline
                                K Offline
                                Kobid
                                wrote on last edited by
                                #16

                                Same result. My model is sorted correctly but QPersistenModelIndex.row() has old value. Don't know if it's ok

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                                • raven-worxR Offline
                                  raven-worxR Offline
                                  raven-worx
                                  Moderators
                                  wrote on last edited by
                                  #17

                                  before further investigating i would recommend that you try "ModelTest":http://qt-project.org/wiki/Model_Test to make sure your model is implemented correctly.

                                  --- SUPPORT REQUESTS VIA CHAT WILL BE IGNORED ---
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                                  • K Offline
                                    K Offline
                                    Kobid
                                    wrote on last edited by
                                    #18

                                    Ehh, can't adjust ModelTest to my model. There are really missing example of QPersistentModelIndex usage. Summarizing, my model is working ok, but don't know why :P . I have this structure:

                                    @struct HCFileItem {
                                    QPersistentModelIndex persistentIndex;
                                    };

                                    class HCFileModel: public QAbstractItemModel
                                    {
                                    Q_OBJECT
                                    public:
                                    explicit HCFileModel(QObject parent=0);
                                    ~HCFileModel();
                                    protected:
                                    QList<HCFileItem
                                    > *mList=0;
                                    };@

                                    Example:

                                    My model contain one item:

                                    "bbbb"

                                    Now I'm inserting (using beginInsertRows) item "aaaa" and my persistent indexes looks like:

                                    "bbbb" (0,0)
                                    "aaaa" (1,0)

                                    Now I'm sorting my model using qSort on mList and emitting signal dataChanged(firstIndex, secondIndex). After this my persistent indexes looks like:

                                    "aaaa" (1,0)
                                    "bbbb" (0,0)

                                    But it works, if I change data in "aaaa" and emit signal dataChanged with saved persistent index in HCFileItem then correct item is refreshed even if QPersistentModelIndex.row() point to wrong row. I'm confused

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                                    • raven-worxR Offline
                                      raven-worxR Offline
                                      raven-worx
                                      Moderators
                                      wrote on last edited by
                                      #19

                                      using ModelTest is as easy (nothing to adjust at all) as:
                                      @
                                      HCFileModel* model = new HCFileModel(parent);
                                      new ModelTest(model, parent);
                                      @
                                      If your model has an error in any state while you use it an assertion will trigger and give you info what went wrong.

                                      --- SUPPORT REQUESTS VIA CHAT WILL BE IGNORED ---
                                      If you have a question please use the forum so others can benefit from the solution in the future

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                                      • K Offline
                                        K Offline
                                        Kobid
                                        wrote on last edited by
                                        #20

                                        Ok my model pass test. So I have no idea why QPersistentModelIndex row() has old value after sort. But everything work, IsValid return True. Must check on QStandardItemModel and QSortFilterProxyModel if persistent index will keep old row too

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                                        • K Offline
                                          K Offline
                                          Kobid
                                          wrote on last edited by
                                          #21

                                          Maybe should I somehow refresh all persistent indexes after sorting?

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