Superclass for ostream and fstream - c++

Question

I'm trying to make my own logging class in C++ using a wrapper class in which i overloaded operator<< that sends it to the cout. Now I want to change it, so that when i create instance of that class, i can pass and argument that logs data in std::cout or some file i create. What is the exact type that is superclass of both fstream and ostream? I tried with std::ios&, std::basic_ios&, std::basic_ostream& and none of them seems to work (throwing me compilation error).
class myostream {
public:
static int getlogLevel() {
return loglevel;
}
static void setlogLevel(int i) {
loglevel = i;
}
myostream(std::basic_ios& cout, int level)
: _cout(cout), _level(level)
{}
template<class T>
std::ostream& operator<<(T t) {
if(_level >= loglevel) {
_cout << loglevelcolor[_level] << loglevelname[_level] << " " << t << COL_RESET << std::endl;
}
return _cout;
}
private:
static int loglevel;
std::basic_ostream& _cout;
int _level;
};

Answer 1

Use base class std::ostream which is typedef for basic_ostream<char>, reference: iostream hierarchy.
Works for me (std::cout, std::ofstream):
#include <iostream>
class myostream {
public:
myostream(std::ostream& out)
: _out(out) {}
template<class T>
std::ostream& operator<<(T t) {
_out << "test" << " " << t << '\n' << 42 << std::endl;
return _out;
}
private:
std::ostream& _out;
};

Answer 2

What is the exact type that is superclass of both fstream and ostream?
It is std::ostream, which is an alias to std::basic_ostream<char>. See the class diagram for std::fstream.
Example:
class myostream {
public:
myostream(int level) // Log into stdout.
: _cout(std::cout), _level(level)
{}
myostream(char const* filename, int level) // Log into a file.
: _file(filename), _cout(_file), _level(level)
{
if(!_file.is_open())
throw std::runtime_error("Failed to open " + std::string(filename));
}
// ...
private:
std::ofstream _file;
std::ostream& _cout;
int _level;
};