QString problem...

[Nefastious]

Hi there guys,

I have a bit of a problem here. I have the following code:

Implementation:

//This function will open the database file (which should lie in the path indicated by the user)
void mainwindow::loaddatabase() {
    //This pretty much says that the database will be of SQLite type, and opens it up from a given path
    QSqlDatabase db = QSqlDatabase::addDatabase("QSQLITE");
    db.setDatabaseName(path);
 
    //This "if" shows up a messagebox in case the program cannot load a given database
    if (!db.open()) {
        QMessageBox::warning(0, qApp->tr("Cannot open database"),
                qApp->tr("Unable to establish a database connection.\n"
                         "This program requires a database to operate. Please contact "
                         "the developer of this software for more information on "
                         "how to use it.\n\n"), QMessageBox::Ok);
    }
 
    //Note: "medadmin" is the name of the table in the SQLite3 database
    model->setTable ("medadmin");
    model->select();
    ...
}

//This function will open the database file (which should lie in the path indicated by the user)
void mainwindow::loaddatabase() {
    //This pretty much says that the database will be of SQLite type, and opens it up from a given path
    QSqlDatabase db = QSqlDatabase::addDatabase("QSQLITE");
    db.setDatabaseName(path);

    //This "if" shows up a messagebox in case the program cannot load a given database
    if (!db.open()) {
        QMessageBox::warning(0, qApp->tr("Cannot open database"),
                qApp->tr("Unable to establish a database connection.\n"
                         "This program requires a database to operate. Please contact "
                         "the developer of this software for more information on "
                         "how to use it.\n\n"), QMessageBox::Ok);
    }

    //Note: "medadmin" is the name of the table in the SQLite3 database
    model->setTable ("medadmin");
    model->select();
    ...
}

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//this makes the openFile dialog get path of the database file and then invocate loaddatabase with such path as the parameter
void mainwindow::openfile() {
 
 path = QFileDialog::getOpenFileName(this,
     tr("Open Database File"), "/Users", tr("SQLite Database File (*.db)"));
 if (!path.isEmpty()){
     loaddatabase();
 }
}

//this makes the openFile dialog get path of the database file and then invocate loaddatabase with such path as the parameter
void mainwindow::openfile() {

 path = QFileDialog::getOpenFileName(this,
     tr("Open Database File"), "/Users", tr("SQLite Database File (*.db)"));
 if (!path.isEmpty()){
     loaddatabase();
 }
}

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This was declared in the header:

class mainwindow : public QMainWindow
{
        //declaring the path variable
        QString path;
        ...
}

class mainwindow : public QMainWindow
{
        //declaring the path variable
        QString path;
        ...
}

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... And it doesn't work! whenever test the program and select a open a .db file he does nothing! I believe that the problem might be associated with the QString path.

Any code with be greatly appreciated

Thanks in advance

[Nefastious]

BUMP

Please help, please...

If any additional information is required please request it

[lasher]

Hi,

Please try to use debugger, set up breakpoint at

if (!path.isEmpty()){
     loaddatabase();

if (!path.isEmpty()){
     loaddatabase();

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and check path value.

[gboelter]

Play with something like this ...

void mainwindow::openfile() 
{
    // for testing only ....
    qDebug() << "we are in openfile() now";
 
    path = QFileDialog::getOpenFileName(this, tr("Open Database File"), "/Users", tr("SQLite Database File (*.db)"));
 
    qDebug() << path;
 
    if ( !path.isEmpty() )
    {
        qDebug() << "path not empty";
        loaddatabase();
    }
    else
    {
        qDebug() << "path is empty";
    {
}

void mainwindow::openfile() 
{
    // for testing only ....
    qDebug() << "we are in openfile() now";

    path = QFileDialog::getOpenFileName(this, tr("Open Database File"), "/Users", tr("SQLite Database File (*.db)"));

    qDebug() << path;

    if ( !path.isEmpty() )
    {
        qDebug() << "path not empty";
        loaddatabase();
    }
    else
    {
        qDebug() << "path is empty";
    {
}

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Regards Guenther

[wysota]

What exactly "doesn't work"?

[Nefastious]

@wysota

it simply doesn't open up any databases, when requested to do so

@at the other guys
will try qdebug and then post another reply with the results

[Nefastious]

well I did play with qDebug for a while it tells me that well, here are the results:

we are in openfile() now
database opened
path not empty

one thing I added qDebug() << "database opened"
as part of that if that tests if the database is opened (in loaddatabase() ),
so aparently the problem doesn't lie in the path String.

Any ideas where it might lie?

If you need any code I will show it upon request

Thanks in advance

[wysota]

Did you try asking the database what the problem was?
QSqlDatabase::lastError()

[Nefastious]

By using

qDebug() << db.lastError();

qDebug() << db.lastError();

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I get the following:

QSqlError(-1, "", "")

What does this mean?

[wysota]

It means there is no error in the database object. How do you know the database failed to open?

[Nefastious]

Well,

there is a model connected to the database and then a TableView connected to the model, and the View remains blank after I supposedly load the database...


Any ideas?

[wysota]

there is a model connected to the database and then a TableView connected to the model, and the View remains blank after I supposedly load the database...

It doesn't mean the database failed to open!

What do QSqlDatabase::open() and QSqlDatabase::isOpen() return?

[Nefastious]

true on both

so we can assume that the problem doesn't lie on the database object itself, but where could it lie? Any ideas?

[wysota]

The query is probably incorrect or the table is empty. Check the last error of the model.

[ChrisW67]

A scope issue? "QSqlDatabase db" goes out of scope at the end of the mainwindow::loaddatabase().

[wysota]

A scope issue? "QSqlDatabase db" goes out of scope at the end of the mainwindow::loaddatabase().

That's irrelevant. SQL databases are kept within a global singleton hash until they are removed by QSqlDatabase::removeDatabase().

[Nefastious]

Sorry to ask but I am unsure how to use qDebug to check for errors in the model (what member should I use?)

Not sure if this will help but here is the code for the view and the model:

//Note: "medadmin" is the name of the table in the SQLite3 database
    model->setTable ("medadmin");
    model->select();
    qDebug << model->error();
 
    //The following lines edit a couple of parameters in the table view "View" and bind it to the model
    ui->View->setWindowTitle ("Patients List");
    ui->View->setModel (model);
    ui->View->setSelectionBehavior (QAbstractItemView::SelectRows);
    ui->View->resizeColumnsToContents();
    ui->View->setSelectionMode (QTableView::SingleSelection);
    ui->View->setVisible (true);
    ui->View->setColumnHidden(0, true);

//Note: "medadmin" is the name of the table in the SQLite3 database
    model->setTable ("medadmin");
    model->select();
    qDebug << model->error();

    //The following lines edit a couple of parameters in the table view "View" and bind it to the model
    ui->View->setWindowTitle ("Patients List");
    ui->View->setModel (model);
    ui->View->setSelectionBehavior (QAbstractItemView::SelectRows);
    ui->View->resizeColumnsToContents();
    ui->View->setSelectionMode (QTableView::SingleSelection);
    ui->View->setVisible (true);
    ui->View->setColumnHidden(0, true);

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[Nefastious]

Note: qDebug << model->error(); is the possible way to use qDebug, it obviously doesn't work, I simply copy+paste'd it by accident... =P