Question

The biggest problem I seem to run into when coding in c++ is the fact that you must declare a class before you can reference it. Say I have two header file like this…

Header1.h

#include "Header2.h"
#include <deque>
#include <string>
#include <iostream>
using namespace std;
class HelloPackage;
class Hello
{
public:
    string Message;
    HelloPackage * Package;
    Hello():Message("")
    {

    }
    Hello(string message, HelloPackage * pack)
    {
        Message = message;
        Package = pack;
    }
    void Execute()
    {
        cout << Message << endl;
        //HelloPackage->NothingReally doesn't exist.
        //this is the issue essentially
        Package->NothingReally(8);
    }
};

Header2.h

#include "Header1.h"
#include <deque>
#include <string>
#include <iostream>
using namespace std;
class HelloPackage
{
public:
    deque<Hello> Hellos;
    HelloPackage()
    {
        Hellos = deque<Hello>();
    }
    int AddHello(string Message)
    {
        Hellos.push_back(Hello(Message,this));
    }
    void ExecuteAll()
    {
        for each(Hello h in Hellos)
            h.Execute();
    }
    int NothingReally(int y)
    {
        int a = 0;
        a += 1;
        return a + y;
    }
}

What I’m wondering is, is there any elegant solution for dealing with these issues? In say c#, and java, you’re not restricted by this “linear” compiling.

Answer 1

1. Use header include guards, either “#ifndef / #define / #endif”, or “#pragma once”
2. Put your code in a .cpp, not inline in the header
3. ???
4. Profit

The reason this will work for you is because you can then use forward declarations of the class you want to reference without including the file if you so wish.