Question

I am not able to find a similar question else where on this site, but is it possible to declare a class over two different files.

for example, all public class components in a file and privates and others in a different file.

publics.h

    class test {
     public:
        int geta();
        void seta(int); 
    };

privates.h

    class test {
     private:
        int a;
    };

The above way is definitely wrong, but is there any such method.

Answer 1

There is a way to get something quite similar: private inheritance.

// private.hpp
class test_details {
  protected:
    int a;
};

// public.hpp

#include "private.hpp"

class test : private test_details {
  public:
    int geta() const { return a; }
    void seta(int i) { a = i; }
};

Note that you will still need to (indirectly) include the private header in any module that uses the public class, so you’re not really hiding anything this way.