I think I'll get right into it and start with the code:
#include <iostream>
#include <fstream>
#include <string>
class test : public std::ofstream
{
public:
test(const std::string& filename) { this->open(gen_filename(filename)); };
test(const test&) = delete;
//test(test&& old) = default; // Didn't compile
test(test&& old) {};
private:
std::string gen_filename(const std::string& filename)
{ return filename + ".tmp"; }
};
int main()
{
auto os = test("testfile");
os << "Test1
";
os << "Test2
";
}
Basically, I need to return an ofstream. Of course you can't copy an ofstream, so I fiddled around with the code in the class test, and I got the above to compile and work as you would expect (on gcc 4.5).
But I have a bad feeling this is just due to my compiler doing "Return Value Optimization" (RTO) on "auto os = test()". Indeed, if modify to the following:
int main()
{
auto os = test("testfile");
os << "Test1
";
auto os2 = std::move(os);
os2 << "Test2
";
}
I no longer get both Test1 and Test2 in the output.
The thing is, the class "test" isn't copyable, so there's no chance of the ofstream being duplicated. I just want to be able to return it from a function. And I seem to be able to do that with GCC.
I'd rather not have dereference smart pointers to a heap allocated ofstream, or reopen the file, as it currently works without doing those things. I just have a feeling I'm being a little "non-standard" in my approach, so a standard way of doing what I've described would be great.
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