class Connection { boost::shared_ptr<MYSQL> m_mysql; public: void connect() { m_mysql.reset(mysql_init(), mysql_close); } bool isConnected() const { return m_mysql.get() != 0; } };
class ConnectionManager { std::map<std::string, Connection> m_connections; public: static ConnectionManager* instance() { static ConnectionManager cm; return &cm; } Connection connection(const std::string& name = "default") { return m_connections[name]; } };
int main() { { Connection c = ConnectionManager::instance()->connection(); std::clog << "isConnected " << c.isConnected() << std::endl; c.connect(); std::clog << "isConnected " << c.isConnected() << std::endl; } Connection c = ConnectionManager::instance()->connection(); std::clog << "isConnected " << c.isConnected() << std::endl;
return 0; }
And the output is:
isConnected 0 MYSQL* mysql_init() isConnected 1 void mysql_close(MYSQL*) isConnected 0
What I don't understand is why shared_ptr calls mysql_close too soon. After all still exists a reference to Connection. I mean, mysql_close should by called when the ConnectionManager singleton is destroyed or am I doing something wrong.
Both c and the map item in ConnectionManager have a shared pointer that points to the "same" MYSQL object, a null. Then you reset c to point to something else. This will not reset the shared pointer in ConnectionManager. Your MYSQL obj gets killed as soon as c goes out of scope. Oliver
- -- Filipe Sousa -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.2 (GNU/Linux)
iD8DBQFDalOEbQdNYqwwwCwRAsNLAJ43BSZTCuraPQ2ouFqGoW/2+JDPDgCeOoQ7 8ZoF4LDO7vQyrPM/Whtx/O8= =iil3 -----END PGP SIGNATURE----- _______________________________________________ Boost-users mailing list Boost-users@lists.boost.org http://lists.boost.org/mailman/listinfo.cgi/boost-users