We don't know what is the file or data that you are "importing".
Perhaps you need some lexer and/or parser to make that import.
Perhaps you could use some existing format, e.g. JSON (for which there are good C++ libraries, like jsoncpp...)
The decision to make (or not) a class -and that is sometimes matter of taste and habits- is unrelated to file import. You could have a class as soon as you have data with member functions operating on it.
But (contrarily to Java) not everything has to be class (or a hierarchy of them). Read also about abstract data types (which could be implemented as one or more classes).
Also understand what is the relation between
class in C++.
Study some free software code related to your project. That could inspire you.
BTW, a C++ header file can, and often does, declare more than one
and it could also define some
static inline functions and
operator, and some
constexpr etc. Many small sized projects (e.g. of less than a hundred thousand lines) have a single header file (which might be precompiled and which would
#include other system or library headers and
#define some macros).
Notice also that standard C++ containers prefer to deal with classes, and you'll better be aware of the rule of five & RAII idiom. If you want a Redis like thing, you might be interested in std::map and/or std::unordered_map etc... and these containers really want classes for their contents (i.e. keys & values).
Understand that a C++ class is cheap. Its instance usually has a some vtable which generally costs only one hidden pointer per instance.