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view not updating automatically

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  • SGaistS SGaist

    That code is a bit surprising. Typically that do loop is completely useless. It's only purpose is to break early if m_list is null which could be done by simply:

    if (m_list == nullptr) {
        return false;
    }
    

    Are you calling setData from your external processing function ?

    JoeCFDJ Offline
    JoeCFDJ Offline
    JoeCFD
    wrote on last edited by JoeCFD
    #10

    @SGaist break is a better option. continue is misleading since there is only one loop.

    if (m_list == nullptr) {
        break;
    }
    

    I guess that default return value is true in his code and return false would be wrong.

    SGaistS 1 Reply Last reply
    0
    • JoeCFDJ JoeCFD

      @SGaist break is a better option. continue is misleading since there is only one loop.

      if (m_list == nullptr) {
          break;
      }
      

      I guess that default return value is true in his code and return false would be wrong.

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

      @JoeCFD my suggestion is to dump that useless loop. As for the return value, you are correct if following the original logic. I would argue that it depends whether the nullptr is an expected value. For me, trying to set data when the container is not present would rather show that there's a logic issue somewhere.

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      Please read the Qt Code of Conduct - https://forum.qt.io/topic/113070/qt-code-of-conduct

      mzimmersM 1 Reply Last reply
      0
      • SGaistS SGaist

        @JoeCFD my suggestion is to dump that useless loop. As for the return value, you are correct if following the original logic. I would argue that it depends whether the nullptr is an expected value. For me, trying to set data when the container is not present would rather show that there's a logic issue somewhere.

        mzimmersM Offline
        mzimmersM Offline
        mzimmers
        wrote on last edited by
        #12

        @SGaist (still looking at your other suggestion.)

        The do {} while (false) loop is a coding convenience. I don't like having multiple return statements in my code, and there are times when I have so many things to test, if I did it with nested if statements, the code would disappear off to the right of the page.

        This approach might seem odd to some, but for me, it's the preferred way to handle such cases.

        JonBJ JoeCFDJ 2 Replies Last reply
        0
        • SGaistS SGaist

          @mzimmers since it's a list, zoneIndex is the row and if you need to add a new row you should use the begin/endInsertRows functions so the update will be triggered automatically.

          mzimmersM Offline
          mzimmersM Offline
          mzimmers
          wrote on last edited by mzimmers
          #13

          @SGaist said in view not updating automatically:

          if you need to add a new row you should use the begin/endInsertRows functions

          Interesting...I don't believe the example in the video used those functions. The list object appendItem function does do this, though:

          bool ZoneList::appendItem(Zone item)
          {
              emit preItemAppended();
              m_list.append(item);
              emit postItemAppended();
          }
          

          and in my model code:

          void ZoneModel::setList(ZoneList *list)
          {
              beginResetModel();
              if (m_list != nullptr) {
                  m_list->disconnect(this);
              }
              m_list = list;
          
              if (m_list != nullptr) {
                  connect(m_list, &ZoneList::preItemAppended, this, [=]() {
                      const int index = m_list->zones().size();
                      beginInsertRows(QModelIndex(), index, index);
                  });
                  connect(m_list, &ZoneList::postItemAppended, this, [=]() {
                      endInsertRows();
                  });
              }
              endResetModel();
          }
          

          So I think it's accomplishing the same thing.

          1 Reply Last reply
          0
          • mzimmersM mzimmers

            @SGaist (still looking at your other suggestion.)

            The do {} while (false) loop is a coding convenience. I don't like having multiple return statements in my code, and there are times when I have so many things to test, if I did it with nested if statements, the code would disappear off to the right of the page.

            This approach might seem odd to some, but for me, it's the preferred way to handle such cases.

            JonBJ Offline
            JonBJ Offline
            JonB
            wrote on last edited by
            #14

            @mzimmers
            I don't think it has anything to do with your present issue, but the code ends up returning true for "successfully changed data" when the list doesn't exist. One would think that returning false here would make more sense. Or initialize your rc to false, set it true when you do something.

            mzimmersM 1 Reply Last reply
            0
            • mzimmersM mzimmers

              @SGaist (still looking at your other suggestion.)

              The do {} while (false) loop is a coding convenience. I don't like having multiple return statements in my code, and there are times when I have so many things to test, if I did it with nested if statements, the code would disappear off to the right of the page.

              This approach might seem odd to some, but for me, it's the preferred way to handle such cases.

              JoeCFDJ Offline
              JoeCFDJ Offline
              JoeCFD
              wrote on last edited by JoeCFD
              #15

              @mzimmers I use it too. It is very convenient in some scenarios. It is kind of different that default value is true. Return true does not seem to mean setting is successful.

              1 Reply Last reply
              0
              • JonBJ JonB

                @mzimmers
                I don't think it has anything to do with your present issue, but the code ends up returning true for "successfully changed data" when the list doesn't exist. One would think that returning false here would make more sense. Or initialize your rc to false, set it true when you do something.

                mzimmersM Offline
                mzimmersM Offline
                mzimmers
                wrote on last edited by mzimmers
                #16

                @JonB that's a good point; I'll probably make that change. Right now, though, that function's never getting called, so I'll leave it be.

                Also, what might be getting lost in this discussion is that most of the ZoneModel updates are working. What is not working is the updating of the equipmentList member of the Zone.

                If this helps, the heirarchy is like this:

                ZoneModel {
                    ZoneList {
                        QList<Zone>
                        
                Zone {
                    QList<QUuid> equipmentUuids
                    
                EquipmentModel {
                    EquipmentList {
                        EquipmentItem {
                            QUuid uiud
                            Qstring name
                            other equipment-specific information
                

                So, I need to:

                • access the ZoneModel
                • traverse its list of zones
                • for each zone, get its list of Uuids
                • for each equipment Uuid, traverse the EquipmentModel to get the additional information about the equipment item.

                I realize this is rather complex, and I'm grateful for any suggestions.

                mzimmersM 1 Reply Last reply
                0
                • mzimmersM mzimmers has marked this topic as solved on
                • mzimmersM mzimmers has marked this topic as unsolved on
                • mzimmersM mzimmers

                  @JonB that's a good point; I'll probably make that change. Right now, though, that function's never getting called, so I'll leave it be.

                  Also, what might be getting lost in this discussion is that most of the ZoneModel updates are working. What is not working is the updating of the equipmentList member of the Zone.

                  If this helps, the heirarchy is like this:

                  ZoneModel {
                      ZoneList {
                          QList<Zone>
                          
                  Zone {
                      QList<QUuid> equipmentUuids
                      
                  EquipmentModel {
                      EquipmentList {
                          EquipmentItem {
                              QUuid uiud
                              Qstring name
                              other equipment-specific information
                  

                  So, I need to:

                  • access the ZoneModel
                  • traverse its list of zones
                  • for each zone, get its list of Uuids
                  • for each equipment Uuid, traverse the EquipmentModel to get the additional information about the equipment item.

                  I realize this is rather complex, and I'm grateful for any suggestions.

                  mzimmersM Offline
                  mzimmersM Offline
                  mzimmers
                  wrote on last edited by
                  #17

                  I think I'm actually fairly close on this, and in fact, the C++ portion of the effort may be working fine. In plain prose, here's what I want to do:

                  for each zone in the ZoneModel:

                  1. get the equipment list for that zone
                    for each equipment list item:
                    2. extract the UUID of that item
                    3. find the item in the EquipmentModel using the UUID above
                    4. extract the name of that item

                  Here's a snippet of the zone-related code:

                  class Zone {
                      Q_GADGET
                      equipmentUuidList m_equipmentList;
                  public:
                      Q_PROPERTY(equipmentUuidList equipmentList MEMBER m_equipmentList)
                  }
                  
                  class ZoneModel: public QAbstractListModel
                  {
                      Q_OBJECT
                  private:
                      ZoneList *m_list;
                  public:
                      Q_INVOKABLE Zone getZone(int index); // gets Zone from list
                  }
                  

                  and the equipment-related code:

                  class EquipmentItem
                  {
                      Q_GADGET
                      Q_PROPERTY(QUuid uuid MEMBER m_uuid READ uuid WRITE setUuid)
                      Q_PROPERTY(QString name MEMBER m_name)
                  
                      QUuid m_uuid;
                      QString m_name;
                  public:
                      Q_INVOKABLE QUuid uuid() const { return m_uuid; };
                      Q_INVOKABLE QString name() const { return m_name; }
                  }
                  
                  class EquipmentModel : public QAbstractListModel
                  {
                      Q_OBJECT
                      Q_PROPERTY(EquipmentList *list READ list WRITE setList NOTIFY listChanged)
                  private:
                      EquipmentList *m_list; // a list of EquipmentItem objects
                  public:
                      EquipmentList *list() { return m_list; }
                      Q_INVOKABLE EquipmentItem getItem(QUuid uuid);
                  }
                  

                  And my QML:

                  ListView {
                  id: scenesView
                  model: zoneModel
                  delegate: Column {
                      property int modelIndex: index
                      property var equipList: zoneModel.getZone(index).equipmentList
                      Text {
                          text: "zone name is " + name
                      }
                      Text {
                          text: "zone UUID is " + uuid
                      }
                  
                      ListView {
                          id: equipment
                          model: equipList
                          delegate: Text {
                              text: "zone equipment name is " + equipmentModel.getItem(WHAT GOES HERE?).name()
                          }
                      }
                  }
                  

                  So...how do I use the uuid extracted in the outer view, as a parameter to getItem() in the inner view?

                  Thanks for reading...

                  mzimmersM 1 Reply Last reply
                  0
                  • mzimmersM mzimmers referenced this topic on
                  • mzimmersM mzimmers

                    I think I'm actually fairly close on this, and in fact, the C++ portion of the effort may be working fine. In plain prose, here's what I want to do:

                    for each zone in the ZoneModel:

                    1. get the equipment list for that zone
                      for each equipment list item:
                      2. extract the UUID of that item
                      3. find the item in the EquipmentModel using the UUID above
                      4. extract the name of that item

                    Here's a snippet of the zone-related code:

                    class Zone {
                        Q_GADGET
                        equipmentUuidList m_equipmentList;
                    public:
                        Q_PROPERTY(equipmentUuidList equipmentList MEMBER m_equipmentList)
                    }
                    
                    class ZoneModel: public QAbstractListModel
                    {
                        Q_OBJECT
                    private:
                        ZoneList *m_list;
                    public:
                        Q_INVOKABLE Zone getZone(int index); // gets Zone from list
                    }
                    

                    and the equipment-related code:

                    class EquipmentItem
                    {
                        Q_GADGET
                        Q_PROPERTY(QUuid uuid MEMBER m_uuid READ uuid WRITE setUuid)
                        Q_PROPERTY(QString name MEMBER m_name)
                    
                        QUuid m_uuid;
                        QString m_name;
                    public:
                        Q_INVOKABLE QUuid uuid() const { return m_uuid; };
                        Q_INVOKABLE QString name() const { return m_name; }
                    }
                    
                    class EquipmentModel : public QAbstractListModel
                    {
                        Q_OBJECT
                        Q_PROPERTY(EquipmentList *list READ list WRITE setList NOTIFY listChanged)
                    private:
                        EquipmentList *m_list; // a list of EquipmentItem objects
                    public:
                        EquipmentList *list() { return m_list; }
                        Q_INVOKABLE EquipmentItem getItem(QUuid uuid);
                    }
                    

                    And my QML:

                    ListView {
                    id: scenesView
                    model: zoneModel
                    delegate: Column {
                        property int modelIndex: index
                        property var equipList: zoneModel.getZone(index).equipmentList
                        Text {
                            text: "zone name is " + name
                        }
                        Text {
                            text: "zone UUID is " + uuid
                        }
                    
                        ListView {
                            id: equipment
                            model: equipList
                            delegate: Text {
                                text: "zone equipment name is " + equipmentModel.getItem(WHAT GOES HERE?).name()
                            }
                        }
                    }
                    

                    So...how do I use the uuid extracted in the outer view, as a parameter to getItem() in the inner view?

                    Thanks for reading...

                    mzimmersM Offline
                    mzimmersM Offline
                    mzimmers
                    wrote on last edited by
                    #18

                    Well, as I suspected, my QML was bad. I got that much figured out:

                    ListView {
                        model: zoneModel
                        delegate: Column {
                            id: infoColumn
                            property int zoneIndex: index
                            property var equipList: (index === 0)
                                                    ? equipmentModel.uuidList()
                                                    : (index > 0)
                                                      ? zoneModel.getZone(index).equipmentList
                                                      : null
                            ListView {
                                height: 80
                                width: 200
                                model: (zoneIndex === 0)
                                       ? equipmentModel.uuidList()
                                       : (zoneIndex > 0)
                                         ? equipList
                                         : null
                                delegate: Text {
                                    property var equipUuid: infoColumn.equipList[index]
                                    text: "zone equipment name is " + equipmentModel.getEquipment(equipUuid).name()
                                }
                            }
                        }
                    }
                    

                    Unfortunately, the auto-update still isn't working. I'll post more on this later.

                    mzimmersM 1 Reply Last reply
                    0
                    • mzimmersM mzimmers

                      Well, as I suspected, my QML was bad. I got that much figured out:

                      ListView {
                          model: zoneModel
                          delegate: Column {
                              id: infoColumn
                              property int zoneIndex: index
                              property var equipList: (index === 0)
                                                      ? equipmentModel.uuidList()
                                                      : (index > 0)
                                                        ? zoneModel.getZone(index).equipmentList
                                                        : null
                              ListView {
                                  height: 80
                                  width: 200
                                  model: (zoneIndex === 0)
                                         ? equipmentModel.uuidList()
                                         : (zoneIndex > 0)
                                           ? equipList
                                           : null
                                  delegate: Text {
                                      property var equipUuid: infoColumn.equipList[index]
                                      text: "zone equipment name is " + equipmentModel.getEquipment(equipUuid).name()
                                  }
                              }
                          }
                      }
                      

                      Unfortunately, the auto-update still isn't working. I'll post more on this later.

                      mzimmersM Offline
                      mzimmersM Offline
                      mzimmers
                      wrote on last edited by mzimmers
                      #19

                      I managed a workaround for this -- In my equipment model, I added an emit to the setData() function:

                      void EquipmentModel::setList(EquipmentList *list)
                      {
                          beginResetModel();
                          if (m_list != nullptr) {
                              m_list->disconnect(this);
                          }
                      
                          m_list = list;
                      
                          if (m_list != nullptr) {
                              connect(m_list, &EquipmentList::preItemAppended, this, [=]() {
                                  const int index = m_list->equipment().size();
                                  beginInsertRows(QModelIndex(), index, index);
                              });
                              connect(m_list, &EquipmentList::postItemAppended, this, [=]() {
                                  emit uuidListChanged(uuidList());
                                  endInsertRows();
                              });
                      
                              connect(m_list, &EquipmentList::preItemRemoved, this, [=](int index) {
                                  beginRemoveRows(QModelIndex(), index, index);
                              });
                              connect(m_list, &EquipmentList::postItemRemoved, this, [=]() {
                                  endRemoveRows();
                              });
                          }
                          endResetModel();
                      }
                      

                      Though I'm not sure why this is necessary, because as @SGaist implied above, the endInsertRows() should have emitted this signal, right?

                      JonBJ 1 Reply Last reply
                      0
                      • mzimmersM mzimmers

                        I managed a workaround for this -- In my equipment model, I added an emit to the setData() function:

                        void EquipmentModel::setList(EquipmentList *list)
                        {
                            beginResetModel();
                            if (m_list != nullptr) {
                                m_list->disconnect(this);
                            }
                        
                            m_list = list;
                        
                            if (m_list != nullptr) {
                                connect(m_list, &EquipmentList::preItemAppended, this, [=]() {
                                    const int index = m_list->equipment().size();
                                    beginInsertRows(QModelIndex(), index, index);
                                });
                                connect(m_list, &EquipmentList::postItemAppended, this, [=]() {
                                    emit uuidListChanged(uuidList());
                                    endInsertRows();
                                });
                        
                                connect(m_list, &EquipmentList::preItemRemoved, this, [=](int index) {
                                    beginRemoveRows(QModelIndex(), index, index);
                                });
                                connect(m_list, &EquipmentList::postItemRemoved, this, [=]() {
                                    endRemoveRows();
                                });
                            }
                            endResetModel();
                        }
                        

                        Though I'm not sure why this is necessary, because as @SGaist implied above, the endInsertRows() should have emitted this signal, right?

                        JonBJ Offline
                        JonBJ Offline
                        JonB
                        wrote on last edited by JonB
                        #20

                        @mzimmers said in view not updating automatically:

                        because as @SGaist implied above, the endInsertRows() should have emitted this signal, right?

                        I am literally walking into this discussion with no context. But what signal should endInsertRows() have emitted according to you? void QAbstractItemModel::rowsInserted(const QModelIndex &parent, int first, int last) will be emitted:

                        Note: This is a private signal. It can be used in signal connections but cannot be emitted by the user.

                        mzimmersM 1 Reply Last reply
                        0
                        • JonBJ JonB

                          @mzimmers said in view not updating automatically:

                          because as @SGaist implied above, the endInsertRows() should have emitted this signal, right?

                          I am literally walking into this discussion with no context. But what signal should endInsertRows() have emitted according to you? void QAbstractItemModel::rowsInserted(const QModelIndex &parent, int first, int last) will be emitted:

                          Note: This is a private signal. It can be used in signal connections but cannot be emitted by the user.

                          mzimmersM Offline
                          mzimmersM Offline
                          mzimmers
                          wrote on last edited by
                          #21

                          @JonB it was my understanding that the code I posted (without my additional emit) was sufficient to automatically update the QML engine when the list changes. But, either I misunderstood that, or there's something wrong with my implementation, because with that extra emit, the app works as desired, and without it, it doesn't.

                          1 Reply Last reply
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                          • mzimmersM mzimmers has marked this topic as solved on

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