C++ forward reference

[Rambetter]

I have two C++ classes, Foo and Bar. Foo is defined in Foo.h and Foo.cc, and Bar is defined in Bar.h and Bar.cc.

Foo is a container for many instances of Bar. Instance methods of Foo return references to instances of Bar. Foo also does some low-level manipulation of Bar's member variables.

However, I have a reference to the container object Foo in every instance of Bar. So, I'm using a forward declaration in Bar.h that looks like this, at the top of that file:

class Foo;

Very simple stuff. This works fine.

Now, I would actually like to do more than just have a reference to Foo inside of Bar. I would like to have access to Foo's innards as well. However, when I try to access any of Foo's innards from Bar, I get a compilation error message that looks like this:

Bar.cc: In member function 'uint16_t Bar::bar() const':
Bar.cc:94: error: invalid use of incomplete type 'const struct Foo'
Bar.h:35: error: forward declaration of 'const struct Foo'
*** Error code 1

To reiterate, I have Foo using Bar's internals and Bar using Foo's internals, both are defined in separate .h and .cc files.

Is this a situation to absolutely avoid, or is there a solution around this?

If needed I will provide code samples, but I don't think it's necessary.

[helios]

So you have this, then:

//foo.h
#include "bar.h"

class Foo{
    Bar a;
};

//bar.h
class Foo;

class Bar{
    Foo &a
};

//foo.cc
#include "foo.h"

//bar.cc 

Right? And you want to use member of Foo from Bar. Just include foo.h in bar.cc (not in bar.h, or you'll have mutually inclusive headers).

[Rambetter]

Wow thank you so much! That works perfect! Should have thought of that myself. For some reason I thought that including it like that was not ``correct''.