ofstream doesn't work when the variable is an attribute - c++

Question

This implementation of ofstream works :
bool LinuxSysCall::addNewUser(std::string const &login, std::string const &password) {
std::ofstream out;
out.open(DATABASEPATH, std::ios::app);
if (out.is_open())
{
std::string str = login + ":" + password + "\n";
std::cout << "writing " << str << std::endl;
out << str;
return true;
}
return false;
}
//The new line is written in the file
But when I put my std::ofstream out as an attribute of LinuxSysCall, it doesn't work anymore (without trowing any exceptions):
bool LinuxSysCall::addNewUser(std::string const &login, std::string const &password) {
this->out.open(DATABASEPATH, std::ios::app);
if (this->out.is_open())
{
std::string str = login + ":" + password + "\n";
std::cout << "writing " << str << std::endl;
this->out << str;
return true;
}
return false;
}
//The new line is not written in the file
Why ?

Answer 1

The destructor of std::ofstream calls close. This will flush the text to the file.
If you want to use a member variable (not "attribute") you would need:
bool LinuxSysCall::addNewUser(std::string const &login,
std::string const &password) {
this->out.open(DATABASEPATH, std::ios::app);
if (this->out.is_open())
{
std::string str = login + ":" + password + "\n";
std::cout << "writing " << str << std::endl;
this->out << str;
this->out.close();
return true;
}
return false;
}
As it stands, using a member variable is much worse than using the local - however, I suspect you actually want to pass the open file around amongst many member functions. If so, you can flush the output with:
this->out << std::flush;
without closing it.