Hi,

I've been struggling quite a while to get 2 classes of different namespace in different header files, knowing each other. The only way I managed to solve this is having a forward declaration right before including the header of the other. I've pasted the code below. While doing this I have a few questions, I hope someone can clarify this;

1. When classes A and B (of different namespaces) need to know each other, why doesn't it work to forward declare them both ways around?

(even though they're only needed as a pointer or const ref)

2. Why does my forward declaration of CD3dscene work without 'being' in the d3drenderer namespace and the renderqueue fwd declaration doesn't work, unless I explicitly place it there, i.e. namespace Crealysm_renderer { class CRenderQueue; }. Fwd declaring "Crealysm_renderer::CRenderQueue' gives an error the Crealysm_renderer is not a known namespace.

Any ideas?

// d3dscene header

#ifndef CD3DSCENE_H
#define CD3DSCENE_H

class Crealysm_d3drenderer::CD3dscene;
#include "Crealysm_renderqueue.h"

namespace Crealysm_d3drenderer
{

class CD3dscene
{
// etc
	//	this only works if the fwd declaration is 'within' the Crealysm_renderer namespace
	//	bool TransformObjects(const Crealysm_renderer::CRenderQueue &pQueue);
	bool TransformObjects(const CRenderQueue &pQueue);
};
}
#endif

// renderqueue header

#ifndef CRENDERQUEUE_H
#define CRENDERQUEUE_H

class CRenderQueue;
#include "Crealysm_d3dscene.h"

namespace Crealysm_renderer
{
class CRenderQueue
{
// etc.
	bool Create(const Crealysm_d3drenderer::CD3dscene *pD3dscene, const int pLightingEffectId);			// changed
};
}
#endif

Thanks, you're absolute right on the namespaces issue, I've solved it now without the unnessary includes:

// header 1

#ifndef CD3DSCENE_H
#define CD3DSCENE_H

namespace Crealysm_IO { class CScene; };
namespace Crealysm_d3drenderer { class CD3dscene; };
namespace Crealysm_renderer { class CRenderQueue; };

// all three headers not included anymore

namespace Crealysm_d3drenderer
{
class CD3dscene
{
public:
	bool TransformObjects(const Crealysm_renderer::CRenderQueue &pQueue);
} // etc

// header 2

#ifndef CRENDERQUEUE_H
#define CRENDERQUEUE_H

#include <vector>

namespace Crealysm_d3drenderer { class CD3dcam; }
namespace Crealysm_renderer	{ class CRenderQueue; }

// etc.

Thanks, I fully agree that rethinking design keeping similar rules & principles in mind, is always a good thing once in a while.

In this case they currently 'need each other', for the following reason:

- D3D scene needs renderqueue pointer because the resulting visible renderable's ID's (after culling) are sent to the renderqueue

- Renderqueue needs pointer to D3D scene because it's the base that fills the queue

I've thought of other options, but in any case at some point some data from the D3Dscene needs to be transferred to the renderqueue. Theoretically I could do this using passing one or more standard types to a 'receiving' generic member function of renderqueue. That way the interdependency would be gone, because d3dscene doesn't need to know renderqueue. In pseudo code:

mRenderQueue.UpdateVisibleIds(pD3dscene->GetIds())