QSqlRelationalTableModel with multiple Joins?

[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....

[devhobby]

@JonB said in QSqlRelationalTableModel with multiple Joins?:

@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.

I'd like to change Table View's flag to Qt::ItemIsEditable... but can't find a way to do it

There's no setFlags() method here...

[JonB]

@devhobby
You have to loop over every item in your table view to make it individually editable (if you're not creating the items yourself, or unless someone suggests a way to cause that to happen as it binds to your model, e.g. https://stackoverflow.com/a/28226056/489865)....

[devhobby]

@JonB said in QSqlRelationalTableModel with multiple Joins?:

@devhobby
You have to loop over every item in your table view to make it individually editable (if you're not creating the items yourself, or unless someone suggests a way to cause that to happen as it binds to your model)....

Suppose I'm inside a for loop where index is a QModelIndex

ui->tableView->model()->data(index). ???

There's no setFlags here still

[JonB]

@devhobby

I think we use QTableWidget, not just QTableView.

http://www.qtcentre.org/threads/46245-QTableWidgetItem-setflags-strange-behavior?p=209282#post209282 shows you accessing QTableWidgetItem. http://doc.qt.io/qt-5/qtablewidget.html#item

http://doc.qt.io/qt-5/qtablewidget.html#details:

The QTableWidget class provides an item-based table view with a default model.
Table widgets provide standard table display facilities for applications. The items in a QTableWidget are provided by QTableWidgetItem.
If you want a table that uses your own data model you should use QTableView rather than this class.

But for QTableView I previously gave you http://www.qtcentre.org/threads/38338-Can-t-edit-my-QTableView-cells?p=176235#post176235:

Qt::ItemFlags MyTableModel::flags (const QModelIndex &index) const
{
   return QAbstractItemModel::flags(index) | Qt::ItemIsEditable;
}

http://doc.qt.io/qt-5/qabstractitemmodel.html#flags, http://doc.qt.io/qt-5/qabstracttablemodel.html#flags works off the model, so presumably your ui->tableView->model()->flags(index).

Ah ha!! Here's what we wanted to know:
http://doc.qt.io/qt-5/qsqlquerymodel.html#details

The model is read-only by default. To make it read-write, you must subclass it and reimplement setData() and flags(). Another option is to use QSqlTableModel, which provides a read-write model based on a single database table.

[devhobby]

@JonB said in QSqlRelationalTableModel with multiple Joins?:

@devhobby

I think we use QTableWidget, not just QTableView.

http://www.qtcentre.org/threads/46245-QTableWidgetItem-setflags-strange-behavior?p=209282#post209282 shows you accessing QTableWidgetItem. http://doc.qt.io/qt-5/qtablewidget.html#item

http://doc.qt.io/qt-5/qtablewidget.html#details:

The QTableWidget class provides an item-based table view with a default model.
Table widgets provide standard table display facilities for applications. The items in a QTableWidget are provided by QTableWidgetItem.
If you want a table that uses your own data model you should use QTableView rather than this class.

But for QTableView I previously gave you http://www.qtcentre.org/threads/38338-Can-t-edit-my-QTableView-cells?p=176235#post176235:

Qt::ItemFlags MyTableModel::flags (const QModelIndex &index) const
{
   return QAbstractItemModel::flags(index) | Qt::ItemIsEditable;
}

At this point I don't even know which of the 2 (table view/table widget) is the most appropriate for my situation.

The last post you linked says to reimplement the method flags() but I don't understand: after inheriting from AbstractItemModel (and reimplementing the method), what am I supposed to do?

[JonB]

@devhobby
Look at the last bit I just added to my post above.

To make it [QSqlQueryModel] read-write, you must subclass it and reimplement setData() and flags().

(And BTW when you've done that there won't be any "iterating over items and setting the editable flag", your items will be editable through your reimplementation of QSqlQueryModel::flags().)

You understand how to "subclass", and how to "reimplement [override] virtual methods", don't you?

[JonB]

@devhobby
I'm going back to your very original post and thinking about what you're actually trying to achieve anyway. The code we're talking about is all well & good, if you want to proceed, but I'm wondering about your expectations of the interface.

In your pic of Employee table only, you have 1 row per employee. When you say:

I want to join the Employee table with EmployeePosition and EmployeeResource so that I can also see, for each employee, their positions and resources (if they have any!)

what are you expecting the table interface to be for the multiple positions & resources you say employees have?

It's all very well to say:

What I need, hence, is a full outer join
The query above gives me everything I want to know and see on the Table View

[I'm trusting that your code implements FULL OUTER JOIN] but left to its own devices this will mean you have many rows per employee, for each position/resource variant. Is that what you intend??

One thing to understand: when you're using QSqlRelationalTableModel so that you can "look up" position/resource names, the combobox you'll get will only ever allow single selection, if you're imagining that it might provide multiple selection it won't.

[devhobby]

@JonB said in QSqlRelationalTableModel with multiple Joins?:

@devhobby
Look at the last bit I just added to my post above.

To make it [QSqlQueryModel] read-write, you must subclass it and reimplement setData() and flags().

(And BTW when you've done that there won't be any "iterating over items and setting the editable flag", your items will be editable through your reimplementation of QSqlQueryModel::flags().)

You understand how to "subclass", and how to "reimplement [override] virtual methods", don't you?

I have my CustomModel class now deriving from QSqlQueryModel

#ifndef CUSTOMMODEL_H
#define CUSTOMMODEL_H
#include <QSqlQueryModel>

class CustomModel : public QSqlQueryModel
{
    Q_OBJECT
    
public:
    bool setData(const QModelIndex &index, const QVariant &value, int role) override;
    Qt::ItemFlags flags(const QModelIndex &index) const override;
};

#endif

The problem is...

The linker somehow can't match the signatures... weird.

I checked this link for example [ https://code.woboq.org/qt5/qtbase/src/corelib/itemmodels/qabstractitemmodel.h.html ]

and both setData() and flags() are the same way I overloaded them...

[JonB]

@devhobby
Now you're talking C++ esotericism, and I'm a Python Qt guy anyway. This one is your problem! :) Sometimes signatures don't match if you don't get your consts just right? What about the Q_INVOKABLE?

https://stackoverflow.com/questions/33781346/how-to-write-setdata-in-qsqlquerymodelqabstractitemmodel is an example of what claims to work? (Oohh, it uses Q_DECL_OVERRIDE for your override?)

[devhobby]

@JonB said in QSqlRelationalTableModel with multiple Joins?:

@devhobby
Oohh, it uses Q_DECL_OVERRIDE for your override?

Yes, it is ALSO that.

Something strange is going on here...

I'll try tagging someone @SGaist @VRonin

--- HEADER FILE ---

#ifndef MYMODEL_H
#define MYMODEL_H

#include <QObject>
#include <QSqlQueryModel>

class MyModel : public QSqlQueryModel
{
    Q_OBJECT

public:
    MyModel(QObject *parent = 0);

    Qt::ItemFlags flags(const QModelIndex &index) const override;
    bool setData(const QModelIndex &index, const QVariant &value, int role = Qt::EditRole) override;
};

#endif // MYMODEL_H

--- CPP FILE ---

#include "mymodel.h"

MyModel::MyModel(QObject *parent) : QSqlQueryModel(parent)
{
}

Qt::ItemFlags MyModel::flags(const QModelIndex &index) const
{

}

bool MyModel::setData(const QModelIndex &index, const QVariant &value, int role)
{

}

[SGaist]

Your CPP file contains an error, the default value should be in the declaration of the function.

If you are using Qt >= 5.7, you can simply use the override keyword as C++11 support is mandatory since that version. Q_DECL_OVERRIDE was used to allow compatibly with non-C++11 enabled compilers.