Use of for_each on map elements

You can iterate through a std::map object. Each iterator will point to a std::pair<const T,S> where T and S are the same types you specified on your map.

Here this would be:

for (std::map<int, MyClass>::iterator it = Map.begin(); it != Map.end(); ++it)
{
  it->second.Method();
}

If you still want to use std::for_each, pass a function that takes a std::pair<const int, MyClass>& as an argument instead.

Example:

void CallMyMethod(std::pair<const int, MyClass>& pair) // could be a class static method as well
{
  pair.second.Method();
}

And pass it to std::for_each:

std::for_each(Map.begin(), Map.end(), CallMyMethod);

C++11 allows you to do:

for (const auto& kv : myMap) {
    std::cout << kv.first << " has value " << kv.second << std::endl;
}

C++17 allows you to do:

for (const auto& [key, value] : myMap) {
    std::cout << key << " has value " << value << std::endl;
}

using structured binding.

UPDATE:

const auto is safer if you don't want to modify the map.