Updating QStandardItemModel when records added to QSQLITE database

gabor53

Hi,
I have a QStandardItemModel displaying records from a db through tableView. How can I update the the records displayed in tableView when a record is added to the db?
Thank you.

VRonin

SQLite has no signaling capabilities (QSqlDriver::hasFeature(QSqlDriver::EventNotifications) == false) so you have 3 alternative routes:

if the database is updated just from your app just emit a signal every time you update it and have a slot refresh the model
if the database is updated just from your app but you can have multiple users/instances running at the same time use QTcpSocket to signal others when something changed
if the database can be changed externally the only choice is to run select from a periodic timer and check the returned table against yours

p3c0

@gabor53
You will also need to update it in the model. There are several methods provided:
http://doc.qt.io/qt-5/qstandarditemmodel.html#setItem
http://doc.qt.io/qt-5/qstandarditemmodel.html#insertRow-1
http://doc.qt.io/qt-5/qstandarditemmodel.html#appendRow-1

gabor53

@VRonin
It is updated only from my app. Do I have to write my own signals and slots?

VRonin

@gabor53

declare a signal in the class that does the update (I presume it's a QObject) and emit it after you perform the update
define a slot that takes care of refreshing the table
connect the two

SGaist

Hi,

Out of curiosity, why not use QSqlTableModel since you are already using QTableView ?

gabor53

@SGaist
I should have

gabor53

@VRonin
is there a tutorial somewhere about custom signals and slots? I wasn't able to find anything recent. Thank you.

VRonin

@gabor53 That's pretty much the core of Qt: http://doc.qt.io/qt-5/signalsandslots.html

gabor53

I came up with the following:
.h file:


signals:
    void RecAdded();

private slots:
    void updateTable();

In cpp:

 connect(on_pushButton_Add_to_DB_clicked(),SIGNAL(recAdded()),this,SLOT(updateTable ()));

The full cpp just in case: cpp

When I try to build it, it gives me the following error message:

C:\Programming\Projects\Folkfriends_1_0\review.cpp:125: error: invalid use of void expression
connect(on_pushButton_Add_to_DB_clicked(),SIGNAL(recAdded()),this,SLOT(updateTable ()));
^
What causes this error? Thank you.

p3c0

@gabor53 The reason is connect expects an object as its first parameter but your on_pushButton_Add_to_DB_clicked() returns a void and thus the error invalid use of void expression
Return an object from that function or use an object directly(makes it more easier to understand).

gabor53

@p3c0
I understand now how it works. In this case the user clicks a button and the record is added to the database. What kind of object do you recommend to create to update the model?

VRonin

You don't have to create any more objects, just replace on_pushButton_Add_to_DB_clicked() with the actual button something like ui->Add_to_DB

gabor53

@VRonin
Thank you. Now I have

connect(ui->pushButton_Add_to_DB,SIGNAL(recAdded()),this,SLOT(updateTable ()));

which works. My new error message is

QObject::connect: No such signal QPushButton::recAdded() in ..\Folkfriends_1_0\review.cpp:125
QObject::connect:  (sender name:   'pushButton_Add_to_DB')
QObject::connect:  (receiver name: 'Review')

In .h I have the following:

signals:
    void RecAdded();

Is this correct?
Thank you.

VRonin

sorry my bad, it should be:

connect(this,SIGNAL(recAdded()),this,SLOT(updateTable ()));

then call emit recAdded() after you added the record in your database

gabor53

@VRonin
I modified like this:

 querys.prepare("INSERT INTO Items (ID, Name, Pic, Description, Month, Day, Year, History, Age, Notes, Color, Material, Signed, What) VALUES(:ID, :Name, :Pic, :Description, :Month, :Day, :Year, :History, :Age, :Notes, :Color, :Material, :Signed, :What)" );
    querys.bindValue (":ID",sIDReview);
    querys.bindValue (":Name",nameReview);
    querys.bindValue (":Pic",fileByteArray);
    querys.bindValue (":Description",descriptionReview);
    querys.bindValue (":Month",monthReview);
    querys.bindValue (":Day",dayReview);
    querys.bindValue (":Year",yearReview);
    querys.bindValue (":History",historyReview);
    querys.bindValue (":Age",ageReview);
    querys.bindValue (":Notes",notesReview);
    querys.bindValue (":Color",colorReview);
    querys.bindValue (":Material",materialReview);
    querys.bindValue (":Signed",SignedbyReview);
    querys.bindValue (":What",whatReview);

    bool result = querys.exec ();

    if(!result)
        {
            qDebug() <<"Error inserting into the main db!" << querys.lastError ();

            QMessageBox::warning (this,"Add to Database Warning","<b><font size='16' color='red'>Error 1002: The Friend was not added to the database.");

        }
    else
        {
            qDebug() << "Entered FunctAdd OK loop.";


            QMessageBox::information (this,"Confirmation","<b><font size = '16' color = 'green'>The Friend was added to the database.</font>");

            emit RecAdded ();
        }

   connect(this,SIGNAL(recAdded()),this,SLOT(updateTable ()));

}

void Review::on_pushButton_Fix_clicked()
{
    Additem *mAdditem = new Additem(this);
    mAdditem->FixFriend (sIDReview, nameReview, whatReview, fileNameReview, materialReview, colorReview, descriptionReview, monthReview, dayReview, yearReview, SignedbyReview, historyReview, ageReview, notesReview);

    mAdditem->show ();
}

void Review::updateTable()
{
    qDebug() << "UpdateTable triggered!";

    MainWindow *myMainWindow = new MainWindow(this);
    myMainWindow->Addview ();
    myMainWindow->show ();
}

It still says
QObject::connect: No such signal Review::recAdded() in ..\Folkfriends_1_0\review.cpp:125
QObject::connect: (sender name: 'Review')
QObject::connect: (receiver name: 'Review')

VRonin

2 problems:

it's case sensitive
the connect "must" be done in the constructor

so in the Review constructor put:

connect(this,&Review::RecAdded,this,&Review::updateTable);

I used the new connect sintax as it's safer

gabor53

This works> Thank you very much.

SGaist

Still, why not change the model to use a more adequate ?

gabor53

@SGaist
I will. Actually I'm doing it now.