Question

I have the following c++ classes:

Page.h:

#ifndef PAGE_H_
#define PAGE_H_

#include "Process.h"

class Page {
public:
    Page();
    virtual ~Page();
    Process *process;
};

#endif /* PAGE_H_ */

and Process.h:

#ifndef PROCESS_H_
#define PROCESS_H_

#include <vector>
#include "Page.h"

class Process {
public:
    Process();
    virtual ~Process();

    int size;
    double life_remaining;
    std::vector<Page> pages;
};

#endif /* PROCESS_H_ */

When I compile I get the following error:

../src/Process.h:21:14: error: ‘Page’ was not declared in this scope
../src/Process.h:21:18: error: template argument 1 is invalid
../src/Process.h:21:18: error: template argument 2 is invalid

How do I correct this?
When I comment out the lines: #include “Proccess.h” and Process *process; then it compiles. When I remove the comments it gives me the error

Answer 1

Use a forward declaration instead of inclusion in Page.h:

//replace this:
//#include "Process.h"

//with this:
class Process;

class Page {
public:
    Page();
    virtual ~Page();
    Process *process;
};