Question

I am creating a class where I defined a Struct called “Room” which I declare as private in the header file. I have several public functions that require a “Room” as an argument. When I compile (in g++) I get an error saying:

Graph.h:42:17: error: "Room" has not been declared

Yet here lies the declaration (whole header file now):

#ifndef GRAPH_H
#define GRAPH_H


#include <iostream>
#include <string>
using namespace std;

class Graph {

public:


    // destructor
    ~Graph();

    // copy constructor
    Graph(const Graph &v);

     // assignment operator
     Graph & operator = (const Graph &v);

    //Create an empty graph with a potential
    //size of num rooms.
     Graph( int num );

        //Input the form:
    //int -- numRooms times
    //(myNumber north east south west) -- numRooms times.
    void input(istream & s);

    //outputs the graph as a visual layout
    void output(ostream & s) const;

    //Recursively searches for an exit path.
    void findPath( Room start );

    //Moves room N E S or W
    void move( Room &*room , String direction );

    //inputs the starting location.
    void inputStart( int start );

    //Searches the easyDelete array for the room with the
    //number "roomNumber" and returns a pointer to it.
    const Room * findRoom( int roomNumber );

private:

    struct Room
    {
        bool visted;
        int myNumber;

        Room *North;
        Room *East;
        Room *South;
        Room *West;
    };

    int numRooms;
    int _index;
    int _start;

    Room ** easyDelete;
    string * escapePath;

    Room * theWALL;
    Room * safety;
};

#endif

Are you not allowed to use structs defined inside the header file as arguments? If so, what’s the workaround?

Thanks.

Answer 1

It compiles fine without the private: header. Why do you have this? Is the struct declared inside of a class?

EDIT

You have used Room before you declare it:

const Room * findRoom( int roomNumber );

Also, you can’t return a Room object through the public method you have declared, since outside code won’t know anything about it.

You need to predeclare it before using it:

class Graph {

public:

struct Room;

const Room * findRoom( int roomNumber );

struct Room
{
    bool visted;
    int myNumber;

    Graph::Room *North;
    Graph::Room *East;
    Graph::Room *South;
    Graph::Room *West;
};

Room room;
};

int main (){

  Graph x;

  return 0;
}

Or you could just move the second private up, above the public section.