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

With the exception of adding overloads to std::swap (the only exception I can think of right now), you are generally not allowed to add anything to the std namespace. Even if it were allowed, the actual declaration for std::vector is a lot more complicated than the code in the OP. See Nikolai N Fetissov's answer for an example.

All that aside, you have the additional problem of what your class users are going to do with functions that return a std::vector or std::string. The C++ Standard section 3.10 says that functions returning such objects are returning rvalues, and rvalues must be of a complete type. In English, if your users want to do anything with those functions, they'll have to #include or > anyway. I think it would be easier to #include the headers for them in your .h file and be done with it.