Question

If I define a pointer-to-map like this:

map<int, string>* mappings;

mappings is a pointer. How should I use this pointer to operate the map?

Answer 1

Use the pointer just like you use any other pointer: dereference it to get to the object to which it points.

typedef std::map<int, string>::iterator it_t;

it_t   it1 = mappings->begin();   // (1)
it_t   it2 = (*mappings).begin(); // (2)

string str = (*mappings)[0];      // (3)

Remember that a->b is — mostly — equivalent to (*a).b, then have fun!

^{(Though this equivalence doesn’t hold for access-by-index like (*a)[b], for which you may not use the -> syntax.)}