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drag-and-drop columns.

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  • NevezN Nevez

    Basically what I want to do is:
    Creating a model over the Mysql database, adding and removing columns in this model, and updating the View again according to this model.

    but, of course, to add/remove columns according to the added/removed index of the labels above

    JonBJ Offline
    JonBJ Offline
    JonB
    wrote on last edited by JonB
    #8

    @Nevez
    Then as that link tells you, you will have to implement your own ADD COLUMN statements for MySQL, whether as part of overriding insertColumns() or not. The supplied SQL driver does not implement it for you (maybe because it varies across SQL implementations, it has many possible options, etc.).

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    • SGaistS Offline
      SGaistS Offline
      SGaist
      Lifetime Qt Champion
      wrote on last edited by
      #9

      What you want to do is called schema alteration. The way that can be done varies depending on the underlying DB system you use. SQLite for example has the ALTER TABLE but that is typically something that you do not do just on a whim.

      Altering a table by adding or removing a column can have far reaching consequences. One simple thing, when you add a new column, what goes in it ? Does it have a default value ? Will it be part of the indexing of the table ? What happens to all the rows that the table contains currently ?

      ORM like Django implements provide facilities to do database migrations and these migrations are steps that you do with care to avoid destroying your current database.

      Interested in AI ? www.idiap.ch
      Please read the Qt Code of Conduct - https://forum.qt.io/topic/113070/qt-code-of-conduct

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      • NevezN Offline
        NevezN Offline
        Nevez
        wrote on last edited by Nevez
        #10

        @SGaist said in drag-and-drop columns.:

        Basit bir şey, yeni bir sütun eklediğinizde içine ne giriyor? Varsayılan bir değeri var mı? Tablonun indekslenmesinin bir parçası olacak mı? Şu anda tablonun içerdiği tüm satırlara ne olur?

        Like the photo I posted above. Each label represents a column in a database. Therefore, when a new column is added, the information of the column with that label text should come from the database.

        likewise for the deleted column; The column with this label text should be detected and deleted from the table.

        So I'm sorry I'll ask again. How exactly should I proceed?

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        • SGaistS Offline
          SGaistS Offline
          SGaist
          Lifetime Qt Champion
          wrote on last edited by
          #11

          Something is highly unclear here.

          Do you want to simply hide and show the corresponding columns in your GUI or alter the table in the database (beside modifying your UI) ?

          Interested in AI ? www.idiap.ch
          Please read the Qt Code of Conduct - https://forum.qt.io/topic/113070/qt-code-of-conduct

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          • NevezN Offline
            NevezN Offline
            Nevez
            wrote on last edited by
            #12

            Of course, if possible, I just want to add hiding through the view. However, since this hiding addition will depend on the column names on the labels, the correct column information must be sent to the right place. So in this case, I think that operations should be done on the model. What do you think?

            JonBJ 1 Reply Last reply
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            • NevezN Nevez

              Of course, if possible, I just want to add hiding through the view. However, since this hiding addition will depend on the column names on the labels, the correct column information must be sent to the right place. So in this case, I think that operations should be done on the model. What do you think?

              JonBJ Offline
              JonBJ Offline
              JonB
              wrote on last edited by JonB
              #13

              @Nevez
              This is not the way to think of it. You do not arrange your base database model/table to suit what you might or might not want to show in a view. Either you want to add new columns of genuine data to the database or you do not. UPDATE Oh, I just saw you only want to hide columns, not add extra ones. Although earlier I thought you were saying you want to add columns.

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              • SGaistS Offline
                SGaistS Offline
                SGaist
                Lifetime Qt Champion
                wrote on last edited by
                #14

                So if it is only visual adding/removing of existing columns, then QTableView's setColumnHidden is what you want to use. With that your model is not affected at all.

                Interested in AI ? www.idiap.ch
                Please read the Qt Code of Conduct - https://forum.qt.io/topic/113070/qt-code-of-conduct

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                • NevezN Offline
                  NevezN Offline
                  Nevez
                  wrote on last edited by Nevez
                  #15

                  yes, this is a good method. but i am wondering if there is any way i can find out this.
                  For example, suppose you have a tableview with 10 columns loaded with a model.
                  When I hide the column in the 5.index with the "hideColumn(5)" method on this tableview,
                  According to the view, the index numbers of the columns after the 5th index should decrease by one.
                  example: (4- [5] --- 6 -7 -8 -9 -10 --->>> 4 - [hided] ---- 5 -6 -7 -8 - 9 )

                  But I check it with visualindex method , index numbers do not changing.
                  but i need to do this. Because When I hide the column, the index numbers of the labels decrease by one because the label in the layout above that column is also hidden.

                  mrjjM 1 Reply Last reply
                  0
                  • NevezN Nevez

                    yes, this is a good method. but i am wondering if there is any way i can find out this.
                    For example, suppose you have a tableview with 10 columns loaded with a model.
                    When I hide the column in the 5.index with the "hideColumn(5)" method on this tableview,
                    According to the view, the index numbers of the columns after the 5th index should decrease by one.
                    example: (4- [5] --- 6 -7 -8 -9 -10 --->>> 4 - [hided] ---- 5 -6 -7 -8 - 9 )

                    But I check it with visualindex method , index numbers do not changing.
                    but i need to do this. Because When I hide the column, the index numbers of the labels decrease by one because the label in the layout above that column is also hidden.

                    mrjjM Offline
                    mrjjM Offline
                    mrjj
                    Lifetime Qt Champion
                    wrote on last edited by
                    #16

                    @Nevez
                    Hi
                    Maybe you can use logical index instead

                    https://uvesway.wordpress.com/2013/01/08/qheaderview-sections-visualindex-vs-logicalindex/

                    Christian EhrlicherC 1 Reply Last reply
                    1
                    • mrjjM mrjj

                      @Nevez
                      Hi
                      Maybe you can use logical index instead

                      https://uvesway.wordpress.com/2013/01/08/qheaderview-sections-visualindex-vs-logicalindex/

                      Christian EhrlicherC Online
                      Christian EhrlicherC Online
                      Christian Ehrlicher
                      Lifetime Qt Champion
                      wrote on last edited by
                      #17

                      @mrjj said in drag-and-drop columns.:

                      Maybe you can use logical index instead

                      Not maybe - it's a must. The visual index is... a visual index so it's not reliable when trying to access the underlying data from the outside.

                      Qt Online Installer direct download: https://download.qt.io/official_releases/online_installers/
                      Visit the Qt Academy at https://academy.qt.io/catalog

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                      • NevezN Offline
                        NevezN Offline
                        Nevez
                        wrote on last edited by Nevez
                        #18

                        my problem is that the visual array doesn't give the result I want.
                        That is, the indexes of the columns to the right of the hided column do not decreasing by one.

                        According to the link @mrjj gave , I guess for this to happen, if I delete a column from the model, The indexes to the right of the deleted column decrease by one.
                        This was a little bad for me.

                        JonBJ 1 Reply Last reply
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                        • NevezN Nevez

                          my problem is that the visual array doesn't give the result I want.
                          That is, the indexes of the columns to the right of the hided column do not decreasing by one.

                          According to the link @mrjj gave , I guess for this to happen, if I delete a column from the model, The indexes to the right of the deleted column decrease by one.
                          This was a little bad for me.

                          JonBJ Offline
                          JonBJ Offline
                          JonB
                          wrote on last edited by
                          #19

                          @Nevez
                          Perhaps you need to give a tiny example illustrating what you claim. Although I haven't used visual indexes, I would expect that after hiding a column the column(s) to the right would have visual indexes one less than the model indexes they show. Note that the model indexes will not change in any way: normally the visual index is the same as the model index, but once you hide a column they will differ. Is that not what you find, or not what your expectation is?

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                          • NevezN Offline
                            NevezN Offline
                            Nevez
                            wrote on last edited by Nevez
                            #20

                            @JonB said in drag-and-drop columns.:

                            I would expect that after hiding a column the column(s) to the right would have visual indexes one less than the model indexes they show.

                            Unfortunately, I tested it, it does not decrease.

                            @JonB said in drag-and-drop columns.:

                            normally the visual index is the same as the model index, but once you hide a column they will differ.

                            No, as I said, when we hide the column, the visual index numbers still do not change (unless we move the columns). So the model index is the same as the visual index.

                            JonBJ 1 Reply Last reply
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                            • NevezN Nevez

                              @JonB said in drag-and-drop columns.:

                              I would expect that after hiding a column the column(s) to the right would have visual indexes one less than the model indexes they show.

                              Unfortunately, I tested it, it does not decrease.

                              @JonB said in drag-and-drop columns.:

                              normally the visual index is the same as the model index, but once you hide a column they will differ.

                              No, as I said, when we hide the column, the visual index numbers still do not change (unless we move the columns). So the model index is the same as the visual index.

                              JonBJ Offline
                              JonBJ Offline
                              JonB
                              wrote on last edited by
                              #21

                              @Nevez
                              OK, I've had a search. This was covered in the https://uvesway.wordpress.com/2013/01/08/qheaderview-sections-visualindex-vs-logicalindex/ reference @mrjj gave you, did you read it?

                              Visual indexes tell us the current position that a given section occupies in the header.

                              However there is a detail one has to be aware of: hiding/showing a given section (calling QHeaderView.hideSection method) does NOT change its visual index as one could expect.

                              So it's perfectly clear: visual indexes are for when you re-order the view columns, but if you only hide a column it (and subsequent columns) still retain their index into the header columns.

                              As I say, I haven't used visual indexes/hiding of columns. But if there is not some better way you would need to write code to map from on-screen-visible columns to underlying column numbers by taking into account which column(s) are hidden where. Which is just some code to write.

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