Breaking cyclic dependency in C++

Question

I have the following cyclic dependency problem I am trying to solve:

typedef std::map<int, my_class> my_map;

class my_class {
...
private:
    my_map::iterator iter;
};

class otherclass{
public:
    my_map::iterator getIter(); 
private:
    my_map map;
};

The compiler does not like this, since my_class was not declared before the typedef.

if I try to forward-declare myclass like this:

class my_class;

typedef std::map<int, my_class> my_map;

class my_class {
...
private:
    my_map::iterator iter;
};

class otherclass{
public:
    my_map::iterator getIter(); 
private:
    my_map map;
};

I get an "error: forward declaration of 'my_class'".

How can I break this vicious cycle?

---

I'm sorry but I have to revise my question, as I have noticed that my representation is slightly wrong.

The following is the correct representation of my problem:

class my_container;

typedef std::map<int, my_container> my_map;

class my_class {
...
private:
    my_map::iterator iter;
};

class my_container {
public:
    my_class a_method();
private:
    vector<my_class> v;
};

class otherclass{
public:
    my_map::iterator a_method();
    my_class another_method();
    my_container yet_another_method();
private:
    my_map map;
};

Sorry about this

Answer 1

put my_map as a member in my_class, like this:

class my_class {
public:     typedef std::map<int, my_class> my_map;
...
private:
        my_map::iterator iter;
};

class otherclass{
public:
        my_class::my_map::iterator getIter(); 
private:
        my_class::my_map map;
};

If you don't want to always use my_class::, then make another typedef.

Answer 2

You could put the typedef inside my_class:

class my_class {
public:
    typedef std::map<int, my_class> my_map;
...
private:
    my_map::iterator iter;
};

class otherclass{
public:
    my_class::my_map::iterator getIter(); 
private:
    my_class::my_map map;
};

Answer 3

class my_class;

typedef std::map  < int, my_class* > my_map;
                      ~~~~~~~~~~ use pointer here!

Answer 4

Circular dependencies are generally a Bad Thing. Can you re-think your design a bit? Does a my_class really need to know what its container is?

If that's not practical, instead of an iterator into my_map, could you get away with just a my_container*? The compiler won't have a problem with using an incomplete type for the pointer.

Answer 5

How about:

#include <map>

class my_class;                         // forward declare the type.
typedef std::map<int, my_class> my_map;

class my_class
{
  private:
    my_map::iterator iter;
};

class otherclass
{
  public:
    my_map::iterator getIter();
  private:
    my_map map;
};