[SOLVED] QT C++ access to a Class Member of another Class

QT C++ access to a Class Member of another Class

i really dont understand the following behavior:

3 Code snippets to explain

sqlconnection.h

class SqlConnection
{
public:
SqlConnection();
QSqlDatabase db;
} ;

sqlconnection.cpp

SqlConnection::SqlConnection()
{ if (!db.open()){ //no different with or without that
  db = QSqlDatabase::addDatabase("QODBC");
  ...
}

artikelverwaltung.cpp

Artikelverwaltung::Artikelverwaltung(){

 SqlConnection().db.open();
 ...(code to do works fine)
}
void Artikelverwaltung::on_pushButton_2_clicked()
{

SqlConnection().db.close(); // "HERE"
}

"HERE" it cycles the full Contructor of the Class again, but why it don't just close the connection? (this is the Main question about and how to fix that.)

I can't even access "db" from another Method inside the Class but outside of the Constructor, like:

sqlconnection.cpp:

void closeDB() {db.close();} is not possible.`

What i am doing wrong?

Thank you guys

Solution

In general, you do not need to use any wrapper class to hold database connections in Qt. You should create a database connection once using QSqlDatabase::addDatabase and open it. After that you can get a database connection anywhere by calling QSqlDatabase::database static method. So to close the database connection you should simply call QSqlDatabase::database().close().