class - c++ how to create classes that are interdependent -

i have storage class. members of class modified. each time member modified, i'd save state of class (clone class instance , save it). i'd create new class, save these states.

for example:

say have storage class in file storage.h

class storage  {  public:    int m_cnt;    <lots of other members...>     storagehistory m_his; }; 

and storagehistory class in file storagehistory.h

class storagehistory  {  public:    std::vector<storage> m_history_vec; }; 

assumptions:

1. storagehistory class should kept in storage class. reason storage class main class can accessed in classes/packages. minimize changes in code, i'd storagehistory coupled storage class.
2. storagehistory cannot static or singleton since multiple instance of storage created.

problems:

1. cannot compile code. storage.h needs compiled before storagehistory.h , vice versa
2. if storagehistory cannot stored in storage class keep it? owner of class?

need define connection between these 2 classed?

first of all: don't make data members public, unless define pure data structure. then: int no c++ type.

now questions: can use forward declarations. since storagehistory used directly in storage, cannot forward declared, storage used in template data member (namely std::vector) in storagehistory, , template not need definition of storage if it's declared variable. need definition when use methods of vector.

so here's untangled code:

storagehistory.h

#include <vector> class storage; class storagehistory  {   std::vector<storage> m_history_vec; public:   /* method declarations */ }; 

storage.h

#include "storagehistory.h" class storage  {   int m_cnt;   /* <lots of other members...> */   storagehistory m_his; public:   /* method declarations */ }; 

storage.cpp

#include "storage.h" #include "storagehistory.h" //not needed, because implicitly included, thats matter of coding style  /* ... storage methods definitions ... */ void storage::changevar(/*...*/) {   m_his.push_back(*this);   /* ... */ } 

storagehistory.cpp

#include "storagehistory.h" #include "storage.h"  /* ... storagehistory method definitions ... */