How can access 'in-memory' sqlite database from QML? - qt

Question

I created an in-memory SQLite database using Qt-C++
const QString m_DRIVER = "QSQLITE";
QSqlDatabase m_db;
m_db = QSqlDatabase::addDatabase(m_DRIVER, "mkddb");
m_db.setDatabaseName(":memory:");
My question is how I can access it in QML?

Answer 1

As long as You have the database connection established in some class of Yours, eg. Database Handler, You can expose it to QML in a very simple way. Here is a very brief concept of how such handler would look like:
DatabaseHandler.h
class DatabaseHandler : public QObject
{
Q_OBJECT
public:
explicit DatabaseHandler(QObject *parent = nullptr);
Q_INVOKABLE void addDatabaseEntry(QString queryString);
private:
QSqlDatabase database = QSqlDatabase::addDatabase("QSQLITE", "mkddb");
QSqlQuery databaseQuery;
};
DatabaseHandler.cpp
DatabaseHandler::DatabaseHandler(QObject *parent) : QObject(parent)
{
database.setDatabaseName(":memory:");
database.open();
databaseQuery = QSqlQuery(database);
}
void DatabaseHandler::addDatabaseEntry(QString queryString)
{
databaseQuery.exec(queryString);
}
The object itself has to be a QObject with a Q_OBJECT macro as on the code above.
To expose the DatabaseHandler to QML, in eg. main.cpp You would have to write this:
qmlRegisterType<DatabaseHandler>("com.organization.databasehandler", 1, 0, "DatabaseHandler");
Then in QML code You can import the database handler and use its methods as long as they're declared with the macro Q_INVOKABLE like in the DatabaseHandler.h:
import com.organization.databasehandler 1.0
ApplicationWindow {
DatabaseHandler {
id: databaseHandler
}
Button {
onClicked: databaseHandler.addDatabaseEntry(/*Query to execute on the database*/)
}
}