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"-almost there" "I can't shake him!" So now that we've got our rendererInterface class defined, we can now just briefly cover how our rendererFactory object will work. To create and initialize a rendererInterface object, we'll need to follow a few steps that we can encapsulate within this factory object. decide which implementation the user wants (ie. OpenGL or Direct3D) use run-time linking to load up the proper DLL create and initialize the rendererInterface object return it for use to the programmer Simple, eh? That's what usually happens when you break down your problem into smaller tasks. //rendererFactory.cpp HRESULT rendererFactory::initInterface(TCHAR *szType) { if(strcmp(szType, "OpenGL") == 0) { //we're using OpenGL for our renderer m_hDLL = LoadLibraryEx("GameOGLRenderer.dll",NULL,0); if(!m_hDLL) { MessageBox(NULL, "Error loading up GameOGLRenderer.dll", "Fatal Error", MB_OK | MB_ICONERROR); return E_FAIL; } } else { //we're using Direct3D for our renderer m_hDLL = LoadLibraryEx("GameD3DRenderer.dll",NULL,0); if(!m_hDLL) { MessageBox(NULL, "Error loading up GameD3DRenderer.dll", "Fatal Error", MB_OK | MB_ICONERROR); return E_FAIL; } } //okay now that we've got our dll loaded, let's get a pointer //to our createInterface function CREATERENDERERINTERFACE CreateInterface = 0; HRESULT hr; CreateInterface = (CREATERENDERERINTERFACE)GetProcAddress(m_hDLL, "createRendererInterface"); hr = CreateInterface(&m_pRenderer); if(FAILED(hr)){ MessageBox(NULL, "Error using our createInterface function", "FATAL Error", MB_OK | MB_ICONERROR); m_pRenderer = NULL; return E_FAIL; } return S_OK; } void rendererFactory::destroyInterface() { DESTROYRENDERERINTERFACE DestroyInterface = 0; HRESULT hr; DestroyInterface = (DESTROYRENDERERINTERFACE)GetProcAddress(m_hDLL, "destroyRendererInterface"); hr = DestroyInterface(&m_pRenderer); if(FAILED(hr)){ MessageBox(NULL, "Error using our destroyInterface function", "GameFramework Error", MB_OK); m_pRenderer = NULL; } } Well, this might look a little complicated, but again, reread the other GameDev.net article on using DLL's and you'll see that it's not so bad. We're just getting a function pointer into our DLL to the proper creating/destroying function. As a reminder, we need to do this in order to deal with the name mangling that accompanies DLL development. What's Included? With this article, I've provided all of the source code listed herein, as well as a TestFramework project, which demonstrates our rendering functionality in action. It's a project built with Visual Studio 6.0. What we learned Well I'm hoping that you had as much fun as I did! We covered quite a bit of material in this article, so hopefully I haven't glossed over things too much. If you have any corrections, or questions, please don't hesitate to email me. References Gamma, Helm, Johnson & Vlissides. Design Patterns: Elements of reusable Object-Oriented Software, Addison Wesley, 1995.

Contents   Introduction   Static .lib and the DLL   Conclusion   Source code   Printable version   Discuss this article The Series   Part I   Part II   Part III   Part IV