Question

I have a situation where I have an instanced class that needs to call a function from the enclosing class. The top class is generated code and compiled after the bottom class is. A consequence is the top class name is not known by the bottom class.

class topClass
{
  public:
    void topFunction();
    bottomCLass * bcInst;
}

class bottomClass
{
  void * owner;
  void someFunction() {owner->topFunction(); }
}

Obviously this won’t work since there’s no definition for topClass.
How can I arrange this so the topClass function can be called from the bottomClass function? I tried using a parent class with a pure virtual function but this crashes when the function is called.

//This is defined and compiled with bottomClass
class classTemplate
{
  public:
    virtual void topFunction()=0;
}

class topClass : public classTemplate
{
  public:
    void topFunction();
    bottomClass * bcInst;
}

class bottomClass
{
  classTemplate * owner;
  void someFunction() {owner->topFunction();//Crashes here }
}

Is there a better way to solve this problem? The one thing I can’t do is give bottom class the name/definition of top class, however the presence and name of topFunction is guaranteed.

Answer 1

Move someFunction() implementation to CPP and include both headers in it. It will help you a lot:

topClass.h:

#ifndef TOPCLASS_H
#define TOPCLASS_H
#include "bottomClass.h"
class topClass
{
  public:
    void topFunction();
    bottomCLass * bcInst;
}
#endif

bottomClass.h:

#ifndef BOTTOMCLASS_H
#define BOTTOMCLASS_H
class bottomClass
{
  void * owner;
  void someFunction();
}
#endif

classes.cpp:

#include "topClass.h"
#include "bottomClass.h"

void bottomClass::someFunction() {owner->topFunction(); }`enter code here`