inheritance - C++ proper way for solve this inheritence include issue "already has a body"? -

heyo, have question issue having in c++. new c++ , learning. have experience in object oriented programming looking correct way , solve issue , why should done way.

classes

i have separated each class interface header file , implementation cpp file.

the first class "alpha" base class:

// a.h #pragma once  class alpha { public:     virtual void myfunction(); }; 

alpha implementation:

// a.cpp #include <iostream> #include "a.h"  void alpha::myfunction() {     std::cout << "class alpha myfunction" << std::endl; } 

i have sub class "beta":

// b.h #pragma once #include "a.h" #include "a.cpp"  class beta : public alpha { public:     virtual void myfunction(); }; 

beta implementation:

// b.cpp #include <iostream> #include "b.h"  void beta::myfunction() {     std::cout << "class beta myfunction" << std::endl; } 

i have manager class called "gamma".

// g.h #pragma once #include <vector> #include "a.h" #include "a.cpp"  class gamma { public:     void run();     std::vector<std::shared_ptr<alpha>> alphacollection; }; 

gamma implementation:

// g.cpp #include "g.h" #include "b.h" #include "b.cpp"  void gamma::run() {     beta localbeta;      alphacollection.push_back(std::make_shared<beta>(localbeta));      // example usage     alphacollection.at(0)->myfunction(); } 

then main:

#include "g.h"; #include "g.cpp";  int main() {     gamma objectg;     objectg.run(); } 

why doing this

the purpose of being want vector of base class alpha in manager can insert elements of varying number of base class objects.

i used beta example of derived class in real implementation have more derived classes such charlie, delta etc.

the goal being manager class gamma able operate on vector elements alpha objects , each of sub classes perform own behavior.

the problem

i cannot compile above example because of how gamma's implementation file includes "g.h" , "b.h" each of include "a.h" , "a.cpp" double including "a.cpp" since has no header guard.

• error c2084: function 'void alpha::myfunction(void)' has body a.cpp
• error c2264: 'alpha::myfunction' : error in function definition or declaration; function not called g.cpp

i have read varying opinions on how use includes , overall feel noob in understanding proper way organize code prevent his.

1. am disorganized?
2. should implementation files use header guards too?
3. should using forward declarations? if how?
4. am crazy want implementation include sub class includes while header includes base class include only?

seriously guidance appreciated!

do not #include cpp files. it's not required , that's causing issue.

#pragma once same include guard - remember it's not portable - it's specific current compiler.

you should not have include guards in cpp files because shouldn't #include them.