I've recently discovered that it is bad form to have #includes in your header files because anyone who uses your code gets all those extra includes they won't necessarily want.

However, for classes that have member variables defined as a type of another class, what's the alternative?

For example, I was doing things the following way for the longest time:

/* Header file for class myGrades */
#include <vector>           //bad
#include "classResult.h"    //bad

class myGrades
{
    vector<classResult> grades;
    int average;
    int bestScore;
}

(Please excuse the fact that this is a highly artificial example)

So, if I want to get rid of the #include lines, is there any way I can keep the vector or do I have to approach programming my code in an entirely different way?