Including header in the class header and implementation?

Question

I have a class Foo with a corresponding .h and .cpp. Both files make use of an std::string. Should I only #include <string> in the header or include it in both files?

Answer 1

if the header can get away with a forward declaration then I always use that in the header and the #include in the implementation file. (FD can be used for reference and pointer types).

If they both need it, then i tend to put them in both so that if the header is changed I can remove it from the .h.