C++, removing #include or #include in class header

Question

I want to remove, if possible, the includes of both and from my class header file. Both string and vector are return types of functions declare

Answer 1

Just include the header in any file where you reference an STL collection.

As others have mentioned, there's not a way to reliably forward declare the STL classes, and even if you find one for your particular implementation, it will probably break if you use a different STL implementation.

If the compilation units don't instantiate the classes, it won't make your object files any bigger.