C++ - Nested include - Avoiding 'include nested too deeply error'

What is the best way of declaring my header files if I want to have the following connections in my C++ code, just so that I don't get the 'include nested too deeply error'?

On my edge class, I have some functions that need to return a Node object. Same for the Edge class, I have functions that need to return a Node object. However the compiler disallow me to have this nested loop thing.

Node.h

#ifndef _NODE_h__
#define __NODE_h__

#include "Edge.h" 
public:
    Node();
    ~Node();
    void setName(string);
    string getName();
    void addEdge(Edge*);
    vector<Edge* > getEdges() { return _edges; };
};
#endif

Edge.h

#ifndef _EDGE_h__
#define __EDGE_h__

#include "Node.h"
class Edge 
{
public:

    Edge();
    Edge(bool);
    ~Edge();
    bool hasBeenSeen() { return _seen; };
    void reset() { _seen = false; };  // resets seen param to false
    Node* getSource() { return _source; };
    Node* getTarget() { return _target; };
    void setSource(Node* source) { _source = source; };
    void setTarget(Node* target) { _target = target; };
};
#endif

Solution

As others have suggested, use header guards. But also try forward declaring the classes in question. You may also have to work with pointers (rather than values) in at least one of your classes, but without seeing the code, we can't tell.

So edge.h should like something like:

#ifndef EDGE_H
#define EDGE_H

class Node;    // forward declaration

Node functionB();

#endif

Note that you will have to define your function in a separate C++ file which then #includes "node.h".

If all this seems very complicated, then you should try simplifying your design. It is probably not necessary for nodes and edges to know about each other — a one way dependency should suffice.

And lastly, names containing double-underscores are reserved in C++ — you are not allowed to create such names in your own code.