Is it possible to handle std::ofstream with std::map?

问题

"Handling map of files in c++" says no, one shall use std::map<std::string, std::ofstream*>, but this leads to the new and delete actions, which is not so neat.

Since "Is std::ofstream movable? Yes!" and it's possible to "std::map<>::insert using non-copyable objects and uniform initialization", is it possible to handle a collection of ofstream using std::map? so that one won't worry about closing filestreams and delete to release memory.

I can compromise that during using std::map<std::string, std::ofstream>, only create, use (it to write) and close, not to copy it.

回答1:

Yes it is possible. See sample code below.

I can compromise that during using std::map<std::string, std::ofstream>, only create, use (it to write) and close, not to copy it.

They are not copyable, so in your final comment, you are correct, you will be unable to copy it. You can move assign though, if that's what you want to do.

#include <iostream>
#include <fstream>
#include <map>

int main()
{
    std::map<std::string, std::ofstream> map;
    map.emplace("foo", std::ofstream("/tmp/foo"));
    map.emplace("bar", std::ofstream("/tmp/bar"));

    map["foo"] << "test";
    map["foo"].flush();

    std::ifstream ifs("/tmp/foo");
    std::string data;
    ifs >> data;

    std::cout << data << '\n';

    return 0;
}

Output:

test

来源：https://stackoverflow.com/questions/40072678/is-it-possible-to-handle-stdofstream-with-stdmap