QSqlRelationalTableModel with multiple Joins?

VRonin

That's correct. Although providing labels/comboboxes is easily implemented via a separate QSqlTableModel/QSqlQueryModel that has all the options and a delegate (in fact that's what QSqlRelationalDelegate does for QSqlRelationalTableModel).

You'd need something like

class RelationDelegate : public QStyledItemDelegate{
    Q_OBJECT
    Q_PROPERTY(QAbstractItemModel* relationModel READ relationModel WRITE setRelationModel NOTIFY relationModelChanged)
    Q_PROPERTY(int keyColumn READ keyColumn WRITE setKeyColumn NOTIFY keyColumnChanged)
    Q_PROPERTY(int valueColumn READ valueColumn WRITE setValueColumn NOTIFY valueColumnChanged)
    Q_PROPERTY(const QPersistentModelIndex& relationModelRoot READ relationModelRoot WRITE setRelationModelRoot NOTIFY relationModelRootChanged)
    Q_DISABLE_COPY(RelationDelegate)
public:
    explicit RelationDelegate(QObject* parent = Q_NULLPTR)
        :QStyledItemDelegate(parent)
        , m_relModel(Q_NULLPTR)
        , m_keyCol(0)
        , m_valueCol(1)
    {
        QObject::connect(this, &RelationDelegate::relationModelChanged, this, &RelationDelegate::viewNeedUpdate);
        QObject::connect(this, &RelationDelegate::keyColumnChanged, this, &RelationDelegate::viewNeedUpdate);
        QObject::connect(this, &RelationDelegate::valueColumnChanged, this, &RelationDelegate::viewNeedUpdate);
        QObject::connect(this, &RelationDelegate::relationModelRootChanged, this, &RelationDelegate::viewNeedUpdate);
    }
    Q_SIGNAL void relationModelRootChanged(const QPersistentModelIndex& rootIdx);
    const QPersistentModelIndex& relationModelRoot() const { return m_relModelRoot; }
    void setRelationModelRoot(const QPersistentModelIndex& rootIdx)
    {
        if (m_relModelRoot == rootIdx)
            return;
        Q_ASSERT(!rootIdx.isValid() || rootIdx.model()==m_relModel);
        m_relModelRoot = rootIdx;
        relationModelRootChanged(m_relModelRoot);
    }
    Q_SIGNAL void viewNeedUpdate();
    QAbstractItemModel* relationModel() const { return m_relModel; };
    Q_SIGNAL void relationModelChanged(QAbstractItemModel* relModel);
    void setRelationModel(QAbstractItemModel* relModel)
    {
        if (relModel == m_relModel) 
            return;
        m_relModel = relModel;
        relationModelChanged(m_relModel);
    }
    int keyColumn() const { return m_keyCol; }
    Q_SIGNAL void keyColumnChanged(int keyCol);
    void setKeyColumn(int keyCol)
    {
        if (keyCol == m_keyCol)
            return;
        m_keyCol = keyCol;
        keyColumnChanged(m_keyCol);
    }
    int valueColumn() const { return m_valueCol; }
    Q_SIGNAL void valueColumnChanged(int valueCol);
    void setValueColumn(int valueCol)
    {
        if (valueCol == m_valueCol) 
            return;
        m_valueCol = valueCol;
        valueColumnChanged(m_valueCol);
    }
    QString displayText(const QVariant& value, const QLocale& locale) const Q_DECL_OVERRIDE{
        if (m_relModel) {
            const int relModelRows = m_relModel->rowCount(m_relModelRoot);
            for (int i = 0; i < relModelRows; ++i) {
                if (m_relModel->index(i, m_keyCol, m_relModelRoot).data() == value)
                    return QStyledItemDelegate::displayText(m_relModel->index(i, m_valueCol, m_relModelRoot).data(), locale);
            }
        }
        return QStyledItemDelegate::displayText(value, locale);
    }
     QWidget* createEditor(QWidget *parent, const QStyleOptionViewItem &option, const QModelIndex &index) const Q_DECL_OVERRIDE{
        if (!m_relModel) 
            return QStyledItemDelegate::createEditor(parent, option, index);
        QComboBox* editor = new QComboBox(parent);
        editor->setModel(m_relModel);
        editor->setRootModelIndex(m_relModelRoot);
        editor->setModelColumn(m_valueCol);
        return editor;
    }
    void setEditorData(QWidget *editor, const QModelIndex &index) const Q_DECL_OVERRIDE{
        if (!m_relModel) 
            return QStyledItemDelegate::setEditorData(editor, index);
        QComboBox* editCombo = qobject_cast<QComboBox*>(editor);
        Q_ASSERT(editCombo);
        const int relModelRows = m_relModel->rowCount(m_relModelRoot);
        for (int i = 0; i < relModelRows; ++i) {
            if (m_relModel->index(i, m_keyCol, m_relModelRoot).data() == index.data()) {
                editCombo->setCurrentIndex(i);
                return;
            }
        }
    }
    void setModelData(QWidget *editor, QAbstractItemModel *model, const QModelIndex &index) const Q_DECL_OVERRIDE{
        if (!m_relModel)
            return QStyledItemDelegate::setModelData(editor, model, index);
        QComboBox* editCombo = qobject_cast<QComboBox*>(editor);
        Q_ASSERT(editCombo);
        const int currIdx = editCombo->currentIndex();
        model->setData(index, m_relModel->index(currIdx, m_keyCol, m_relModelRoot).data());
    }
    void updateEditorGeometry(QWidget *editor, const QStyleOptionViewItem &option, const QModelIndex &index) const Q_DECL_OVERRIDE{
        if (!m_relModel)
            return QStyledItemDelegate::updateEditorGeometry(editor, option, index);
        editor->setGeometry(option.rect);
    }
    
private:
    QAbstractItemModel* m_relModel;
    int m_keyCol;
    int m_valueCol;
    QPersistentModelIndex m_relModelRoot;
};

and connect the viewNeedUpdate to the update of the view

JonB

@VRonin
Yes. I appreciate this. Like I edited my previous, it's actually the QSqlTableModel level I miss, QSqlRelationalTableModel doesn't add that much. I realize each one is written on top of the next one in Qt, so of course you can design them on top of QSqlQuery.

That's a bit of code you've written there! It'll be even more to model QSqlTableModel too :)

devhobby

I wanted to take a different approach:

Send a custom query to the table view in read-only mode

Then, a right click (or another method) will change the content of the record through code.

The problem is: I can't even send a custom query!

My query (similar to the one I posted above) has some joins in it.

But why can't I use the table returned by a query as the table to display on the Table View?

Is all this really so limited?

JonB

@devhobby
You are using a QTableView, right? You can use that against a QSqlQueryModel, which is a model based against a query rather than an actual table.

devhobby

@JonB said in QSqlRelationalTableModel with multiple Joins?:

@devhobby
You are using a QTableView, right? You can use that against a QSqlQueryModel, which is a model based against a query rather than an actual table.

No, I'm using a QSqlQueryModel

        _queryModel = new QSqlQueryModel(ui->tableView);

       _queryModel->setQuery("SELECT Employee.id, Employee.Name, Employee.Surname, Birthplace.Name as 'Birthplace', Employee.Birthdate, Residence.Name as 'Residence', Employee.Qualification, Position.Name as 'Position', EmployeePosition.EngagementDate, Resource.Name as 'Resource', EmployeeResource.AcquisitionDate"
                    "FROM Employee"
                    "LEFT JOIN EmployeePosition ON Employee.id = EmployeePosition.idEmployee"
                    "LEFT JOIN Position ON EmployeePosition.idPosition = Position.id"

                    "LEFT JOIN EmployeeResource ON Employee.id = EmployeeResource.idEmployee"
                    "LEFT JOIN Resource ON Resource.id = EmployeeResource.idResource"

                    "LEFT JOIN Country AS Birthplace ON Employee.BirthplaceID = Birthplace.id"
                    "LEFT JOIN Country AS Residence ON Employee.ResidenceID = Residence.id", *_db);

        ui->tableView->setModel(_queryModel);
        ui->tableView->show();

And the Table View is blank

I also tried with QSqlTableModel

        _tableModel = new QSqlTableModel(ui->tableView, *_db);

        QString myQuery = "SELECT Employee.id, Employee.Name, Employee.Surname, Birthplace.Name as 'Birthplace', Employee.Birthdate, Residence.Name as 'Residence', Employee.Qualification, Position.Name as 'Position', EmployeePosition.EngagementDate, Resource.Name as 'Resource', EmployeeResource.AcquisitionDate"
                        "FROM Employee"
                        "LEFT JOIN EmployeePosition ON Employee.id = EmployeePosition.idEmployee"
                        "LEFT JOIN Position ON EmployeePosition.idPosition = Position.id"

                        "LEFT JOIN EmployeeResource ON Employee.id = EmployeeResource.idEmployee"
                        "LEFT JOIN Resource ON Resource.id = EmployeeResource.idResource"

                        "LEFT JOIN Country AS Birthplace ON Employee.BirthplaceID = Birthplace.id"
                        "LEFT JOIN Country AS Residence ON Employee.ResidenceID = Residence.id";

        _tableModel->setTable(myQuery );
        _tableModel->setEditStrategy(QSqlTableModel::OnManualSubmit);
        _tableModel->select();

        ui->tableView->setModel(_tableModel);
        ui->tableView->show();

Same issue: Table View is blank.

JonB

@devhobby
I was asking you to confirm that in ui->tableView->setModel(_queryModel); the type of your ui->tableView is a QTableView?

Anyway, assuming it is, what's this:

 _queryModel = new QSqlQueryModel(ui->tableView);

What's that parent doing there? (Haven't seen this before, just checking.)

Does QSqlQueryModel::lastError() tell you anything after setQuery() or later?

Hang on! I don't do C++, but the way you've written your query, does C++ join the strings with a space between? Because if not (and I don't think it does) your words are all touching each other, and you have a SQL error!! Make sure your query is right, and check that lastError() thing, e.g.

QSqlQueryModel model;
model.setQuery("select *"
               "from MyTable");
if (model.lastError().isValid())
    qDebug() << model.lastError();

Because I think the principle should be working fine otherwise.

devhobby

@JonB said in QSqlRelationalTableModel with multiple Joins?:
does C++ join the strings with a space between? Because if not (and I don't think it does) your words are all touching each other, >and you have a SQL error!! Make sure your query is right, and check that lastError() thing, e.g.
Because I think the principle should be working fine otherwise.

Oh gosh! I completely forgot to put the spaces before each line! Thanks

By the way, once that I get all of this setup... now I need to find a way to customize a cell (item).
I successfully retrieve its index... but I'd like to change its background color, for instance

And since I'm using a Table View and not a Table Widget, I only see item delegates.

How can I achieve what I want?

VRonin

See https://forum.qt.io/topic/85973/how-to-simply-change-the-background-colour-of-a-cell-inside-a-tableview

devhobby

@VRonin said in QSqlRelationalTableModel with multiple Joins?:

See https://forum.qt.io/topic/85973/how-to-simply-change-the-background-colour-of-a-cell-inside-a-tableview

Thanks but before doing that, I was wondering if there's a way to change the content of the cell by directly typing into it.

I just want to change the data of the cell and, once changed, color that cell in a different color to alert the user of the change of that particular item/cell.

Seems a lot of hard-coding work... maybe I should find another convenient way... but for now let's see what comes out

JonB

@devhobby
If you want to edit in a QTableView (right?), what have you set your http://doc.qt.io/qt-5/qabstractitemview.html#editTriggers-prop to?

devhobby

@JonB said in QSqlRelationalTableModel with multiple Joins?:

@devhobby
If you want to edit in a QTableView (right?), what have you set your http://doc.qt.io/qt-5/qabstractitemview.html#editTriggers-prop to?

QAbstractItemView::DoubleClicked

ui->tableView->setModel(_queryModel);
ui->tableView->verticalHeader()->hide();
ui->tableView->setEditTriggers(QAbstractItemView::DoubleClicked);
ui->tableView->show();

JonB

@devhobby
And you are saying that when you double-click...? Nothing at all happens?

If that is the case, I can only imagine your model is read-only, to do with it being a SELECT and not a table? To be clear, you won't be "changing the data of the cell" per se, you'll be changing the data in the model that cell is displaying.

devhobby

@JonB said in QSqlRelationalTableModel with multiple Joins?:

@devhobby
And you are saying that when you double-click...? Nothing at all happens?

If that is the case, I can only imagine your model is read-only, to do with it being a SELECT and not a table?

Yes, as stated above I used my custom query to do all the joins.

By the way, I don't expect to change the database directly.

I just want to visually edit the cell without applying any changes to the database.

Once the user changes the text of the cell, the new text is immediately visible and I store it in a QString

When the user presses the button "Commit changes" I will have a series of changes that the user wants to apply to the database -> I now need to make them real sending a custom query to the database.

JonB

@devhobby
I'm a little lost. You wrote:

Thanks but before doing that, I was wondering if there's a way to change the content of the cell by directly typing into it.

I thought you were saying when double-click it does not let you edit, nothing happens, or whatever. Now I think you're saying it does let you edit? I don't know if you have a question here?

devhobby

@JonB said in QSqlRelationalTableModel with multiple Joins?:

@devhobby
I'm a little lost. You wrote:

Thanks but before doing that, I was wondering if there's a way to change the content of the cell by directly typing into it.

I thought you were saying when double-click it does not let you edit, nothing happens, or whatever. Now I think you're saying it does let you edit? I don't know if you have a question here?

Yes I asked if there's a way to change the content of the cell by directly typing into it

Because now, when I double click, nothing happens.

Once the cell is edited, I'd also like to change its background color... but that's another story

JonB

@devhobby said in QSqlRelationalTableModel with multiple Joins?:

Once the user changes the text of the cell, the new text is immediately visible and I store it in a QString

Because now, when I double click, nothing happens.

Sorry, but if "nothing happens" when you double-click cell to edit, how come you talk about "Once the user changes the text of the cell"? Maybe I'm being dumb, but I just don't get it!

devhobby

@JonB said in QSqlRelationalTableModel with multiple Joins?:

@devhobby said in QSqlRelationalTableModel with multiple Joins?:

Once the user changes the text of the cell, the new text is immediately visible and I store it in a QString

Because now, when I double click, nothing happens.

Sorry, but if "nothing happens" when you double-click cell to edit, how come you talk about "Once the user changes the text of the cell"? Maybe I'm being dumb, but I just don't get it!

Don't worry! I'm sorry, I'm probably using the wrong tenses to express myself.

"Once the user changes the text of the cell, the new text is immediately visible and I store it in a QString"

Is the prediction of what I want to happen... and can't manage to make it happen actually

JonB

@devhobby

Is the prediction of what I want to happen... and can't manage to make it happen actually

Ohhhh...! :)

OK, I would expect you've done the right stuff. I believe that's what our code does. I can only think of what I suggested: that the SELECT makes the model read-only, and editing is not allowed.

I shall step aside and you need an expert here to guide you further....

devhobby

@JonB said in QSqlRelationalTableModel with multiple Joins?:

@devhobby

Is the prediction of what I want to happen... and can't manage to make it happen actually

Ohhhh...! :)

OK, I would expect you've done the right stuff. I believe that's what our code does. I can only think of what I suggested: that the SELECT makes the model read-only, and editing is not allowed.

I shall step aside and you need an expert here to guide you further....

Yes, the custom query is most likely keeping my Table View read-only.

I just want to visually edit the cells...

This is far more complicated than I thought...

JonB

@devhobby
http://doc.qt.io/qt-5/qitemdelegate.html#details must be to do with it.

I could easily be wrong(!), but I thought the idea of the model/view would be that if you edit it would save the value back to the model, not "just give you some string". You can doubtless play with the delegate to do something else...

P.S.
Look at http://www.qtcentre.org/threads/38338-Can-t-edit-my-QTableView-cells:

Check if the item is actually editable: (MyTable->model()->flags(idx) & Qt::ItemIsEditable). If not, make it so.

https://stackoverflow.com/questions/28186118/how-to-make-qtableview-to-enter-the-editing-mode-only-on-double-click:

Setting a Qt.ItemIsEnabled flag makes the QTableView items editable. To enter the item's editing mode the user can simply double-click it.

EDIT: You have to loop over every item in your table view to make it individually editable....