C++: Printing out map values - c++

Question

So I have a map like this:
map<long, MusicEntry> Music_Map;
MusicEntry contains strings of (name, artist, size, and date added)
My question is how can print, how do I print out all the data in my map? I have tried doing...
for(auto it = Music_Map.cbegin(); it!= Music_Map.cend(); ++it)
cout << it-> first << ", " << it-> second << "\n";
I think the problem is occuring that it can't compile and read second aka MusicEntry..

Answer 1

You need to provide an std::ostream operator<< (std::ostream&, const MusicEntyr&) so that you can do this kind of thing:
MusicEntry m;
std::cout << m << std::endl;
With that in place, you can print the map's second fields. Here's a simplified example:
struct MusicEntry
{
std::string artist;
std::string name;
};
std::ostream& operator<<(std::ostream& o, const MusicEntry& m)
{
return o << m.artist << ", " << m.name;
}

Answer 2

The code you have is fine, but you need to implement
std::ostream& operator<<(ostream& os, const MusicEntry& e)
{
return os << "(" << e.name << ", " << ... << ")";
}
and you probably need to declare the above a friend in MusicEntry to access the private (or protected) data of MusicEntry:
class MusicEntry
{
// ...
friend std::ostream& operator<<(ostream& os, const MusicEntry& e);
};
This is, of course, not needed if the data is public or if you use public getters. You can find a lot more information in the operator overloading FAQ.