Forward declaring a private struct

[armstrhu]

Hello forum,
I have a question on gaining access to a private struct via forward declaration. I have a class such as

class foo
{
  public:
   ...
   bar::iterator begin() {return my_bar.begin();}
   bar::iterator end() {return my_bar.end();}

  private:
    ...
    struct bar
    {
      typedef std::vector<float>::iterator iterator;
      iterator begin(){return my_data.begin();}
      iterator end(){return my_data.end();}

      private:
        std::vector<float> my_data;
    };
    bar my_bar;
}

the code wont compile because in the public section it does not yet know about the struct bar. The code works if I just flip the definitions such that the private: section comes before the public: section. But, I was wondering if there is another way to get around this so that I can keep the organization public:, protected:, private:? Thanks!

[MiiNiPaa]

No. It follows nomal rules where entity should be defined before use.

[armstrhu]

Ok thank, yeah I tried a few things and couldn't get it to work. I have another similar question. Can I forward declare bar and implement it outside of the class foo? I have tried and it also does not seem to work...something along these lines

class foo
{
  private:
    ...
    struct bar; //Forward declare bar???
    bar my_bar;

  public:
   ...
   bar::iterator begin() {return my_bar.begin();}
   bar::iterator end() {return my_bar.end();}
}

struct foo::bar
{
  typedef std::vector<float>::iterator iterator;
  iterator begin(){return my_data.begin();}
  iterator end(){return my_data.end();}

  private:
    std::vector<float> my_data;
};

[MiiNiPaa]

you can forward declare bar, but you can use it only as other forward declaration: declaring and moving around pointers and references to that class. To use nested types and member functions, you need to define class itself before use.