QSQL, Create a factory for connections

[Exotic_Devel]

I tried to create a singleton class that will act as a connection factory. In theory it should create a new connection when your method "connection" is called.

The code I was able to write this:

@/*

• dataaccess.hpp
• This file is part of TecTracker
• Copyright (C) 2014 - Matheus
• TecTracker is free software; you can redistribute it and/or modify
• it under the terms of the GNU General Public License as published by
• the Free Software Foundation; either version 2 of the License, or
• (at your option) any later version.
• TecTracker is distributed in the hope that it will be useful,
• but WITHOUT ANY WARRANTY; without even the implied warranty of
• MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
• GNU General Public License for more details.
• You should have received a copy of the GNU General Public License
• along with TecTracker. If not, see http://www.gnu.org/licenses/.
  */

/Classe singleton/

#ifndef DATAACCESS_HPP
#define DATAACCESS_HPP
#include<QtSql/QSqlDatabase>
#include<QObject>

class DataAccess
{
public:
static DataAccess* instance(); /* <= Devolve um objeto do tipo DataAccess*/
QSqlDatabase* conection(QSqlDatabase cnx, QObject evoker = 0); /<= Método para obter uma conexão/

private:
explicit DataAccess();
DataAccess(const DataAccess&);
DataAccess& operator=(const DataAccess&);
static DataAccess dataaccess; / <= Objeto DataAccess*/

};

#endif // DATAACCESS_HPP
@

@/*

• dataaccess.cpp
• This file is part of TecTracker
• Copyright (C) 2014 - Matheus
• TecTracker is free software; you can redistribute it and/or modify
• it under the terms of the GNU General Public License as published by
• the Free Software Foundation; either version 2 of the License, or
• (at your option) any later version.
• TecTracker is distributed in the hope that it will be useful,
• but WITHOUT ANY WARRANTY; without even the implied warranty of
• MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
• GNU General Public License for more details.
• You should have received a copy of the GNU General Public License
• along with TecTracker. If not, see http://www.gnu.org/licenses/.
  */

#include <QMutex>
#include "dataaccess.hpp"

DataAccess *DataAccess::dataaccess; /DataAccess object null/

DataAccess* DataAccess::instance()
{
static QMutex mutex;

if(!dataaccess)
{
mutex.lock();

  if(!dataaccess)
    dataaccess = new DataAccess;

  mutex.unlock();

}
return dataaccess;
}

QSqlDatabase* DataAccess::conection(QSqlDatabase *cnx, QObject *evoker )
{
if(evoker)
*cnx = QSqlDatabase::addDatabase("QPSQL", evoker->objectName().append("cnx")); /Namede conection/
else
*cnx = QSqlDatabase::addDatabase("QPSQL"); /Default conection/

cnx->setDatabaseName("tectracker");
cnx->setUserName("");
cnx->setPassword("");
cnx->setPort(***);
cnx->setHostName("*****");

return cnx;
}

DataAccess::DataAccess() /Private Constructor/
{
}
@

However, I am getting signal 11 and fatal error during unit testing.
When I trigger the debug, I get Signal name: SIGSEGV and Signal meaning: Segmentation fault

The debug indicates the line:

@*cnx = QSqlDatabase::addDatabase("QPSQL", evoker->objectName().append("cnx")); /Namede conection/@

I believe I'm using pointers incorrectly, but not sure.

[Exotic_Devel]

I believe that the error was in how I called the method:

@ QSqlDatabase *objdata;

QFETCH(QObject*, parente);
QFETCH(bool, banco);
QCOMPARE(DataAccess::instance()->conection(&objdata, parente)->open(), banco);@

I switched to

@QSqlDatabase objdata;

QFETCH(QObject*, parente);
QFETCH(bool, banco);
QCOMPARE(DataAccess::instance()->conection(&objdata, parente)->open(), banco);@

Thus there is no more the error.

What was wrong in the previous form?

[Exotic_Devel]

Ok, I think I understood. Thanks to: http://en.wikipedia.org/wiki/Segmentation_fault

In the first case I was stored the returned object of QSqlDatabase::addDatabase on a non-existent address

Since @QSqlDatabase * objdata;@ does not define an address