qt mysql connection error - c++

Question

i am testing out a database connection on QT but i get this error
[root#server env]# make
g++ -c -m64 -pipe -O2 -g -pipe -Wall -Wp,-D_FORTIFY_SOURCE=2 -fstack-protector --param=ssp-buffer-size=4 -m64 -mtune=generic -Wall -W -D_REENTRANT -DQT_NO_DEBUG -DQT_GUI_LIB -DQT_CORE_LIB -I../../../lib64/qt4/mkspecs/linux-g++-64 -I. -I../../../include/QtCore -I../../../include/QtGui -I../../../include -I. -I. -o test.o test.cpp
test.cpp: In function ‘int main()’:
test.cpp:20: error: cannot convert ‘QSqlDatabase’ to ‘int’ in return
test.cpp: At global scope:
test.cpp:23: error: ‘Database’ has not been declared
make: *** [test.o] Error 1
this is the code:
#include <stdlib.h>
#include <iostream>
#include "/usr/include/mysql/mysql.h"
#include <QDebug>
#include <QtSql/QtSql>
using namespace std;
int main() {
cout << "SHELL = " << getenv("SHELL") << endl;
cout << "SHELL = " << getenv("TERM") << endl;
QSqlDatabase db = QSqlDatabase::addDatabase("QMYSQL");
db.setHostName("xxx.xxxx.xxxx.xxx");
db.setDatabaseName("SAMS");
db.setUserName("xxxxxxxx");
db.setPassword("xxxxxxxxxx");
if (!db.open()) qDebug() << "Failed to connect to mysql as user testuser";
return db;
}
void Database::closeDb(){
QSqlDatabase::removeDatabase("QMYSQL");
}
any idea???
UPDATE:
#include <stdlib.h>
#include <iostream>
#include "/usr/include/mysql/mysql.h"
#include <QDebug>
#include <QtSql/QtSql>
using namespace std;
void conn() {
cout << "SHELL = " << getenv("SHELL") << endl;
cout << "SHELL = " << getenv("TERM") << endl;
QSqlDatabase db = QSqlDatabase::addDatabase("QMYSQL");
db.setHostName("xxxxxxxx");
db.setDatabaseName("xxxxxxxx");
db.setUserName("xxxxx");
db.setPassword("xxxxxxxxxx");
if (!db.open()) qDebug() << "Failed to connect to mysql as user testuser";
}
void closeDb(){
QSqlDatabase::removeDatabase("QMYSQL");
}
[root#server env]# make
g++ -c -m64 -pipe -O2 -g -pipe -Wall -Wp,-D_FORTIFY_SOURCE=2 -fstack-protector --param=ssp-buffer-size=4 -m64 -mtune=generic -Wall -W -D_REENTRANT -DQT_NO_DEBUG -DQT_GUI_LIB -DQT_CORE_LIB -I../../../lib64/qt4/mkspecs/linux-g++-64 -I. -I../../../include/QtCore -I../../../include/QtGui -I../../../include -I. -I. -o test.o test.cpp
g++ -m64 -Wl,-O1 -o env test.o -lQtGui -lQtCore -lpthread
/usr/lib/gcc/x86_64-redhat-linux/4.4.6/../../../../lib64/crt1.o: In function `_start':
(.text+0x20): undefined reference to `main'
test.o: In function `closeDb()':
/usr/local/dev/env/test.cpp:23: undefined reference to `QSqlDatabase::removeDatabase(QString const&)'
test.o: In function `QString':
/usr/include/QtCore/qstring.h:683: undefined reference to `QSqlDatabase::defaultConnection'
test.o: In function `conn()':
/usr/local/dev/env/test.cpp:14: undefined reference to `QSqlDatabase::addDatabase(QString const&, QString const&)'
/usr/local/dev/env/test.cpp:15: undefined reference to `QSqlDatabase::setHostName(QString const&)'
/usr/local/dev/env/test.cpp:16: undefined reference to `QSqlDatabase::setDatabaseName(QString const&)'
/usr/local/dev/env/test.cpp:17: undefined reference to `QSqlDatabase::setUserName(QString const&)'
/usr/local/dev/env/test.cpp:18: undefined reference to `QSqlDatabase::setPassword(QString const&)'
/usr/local/dev/env/test.cpp:19: undefined reference to `QSqlDatabase::open()'
/usr/local/dev/env/test.cpp:19: undefined reference to `QSqlDatabase::~QSqlDatabase()'
/usr/local/dev/env/test.cpp:19: undefined reference to `QSqlDatabase::~QSqlDatabase()'
/usr/local/dev/env/test.cpp:14: undefined reference to `QSqlDatabase::~QSqlDatabase()'
collect2: ld returned 1 exit status
make: *** [env] Error 1
update:
this worked..
#include <stdlib.h>
#include <iostream>
#include "/usr/include/mysql/mysql.h"
#include <QDebug>
#include <QtSql/QtSql>
using namespace std;
void conn() {
QSqlDatabase db = QSqlDatabase::addDatabase("QMYSQL");
db.setHostName("xxxxxxxxxxx");
db.setDatabaseName("SAMS");
db.setUserName("xxxxxxxx");
db.setPassword("xxxxxxxx");
if (!db.open()) {
qDebug() << "Failed to connect to mysql as user testuser";
}
else {
qDebug() << "hello";
}
}
void closeDb() {
QSqlDatabase::removeDatabase("QMYSQL");
}
int main() {
cout << "SHELL = " << getenv("SHELL") << endl;
cout << "SHELL = " << getenv("TERM") << endl;
conn();
return 0;
}
i had to add
QT += core gui sql
to the project file..

Answer 1

You are returning your QSqlDatabase in your int main() function and this is invalid because QSqlDatabase is not int. Why are you returning it? If you want the return type to describe success then use -1 and otherwise 0, for instance.
As for the second error, you haven't any class defined called Database so you can't define the method Database::closeDb(). Instead create a function to do what you want:
void closeDb() {
QSqlDatabase::removeDatabase("QMYSQL");
}
But I don't see the purpose of closeDb() when you are not using it anyway.