Writing COM components in pure C + +

This article provides an in-process (DLL) COM server that is fully implemented in C + + and does not provide any support for ATL or MFC. Writing COM objects in this way gives you insight into how COM processes the server in-process and how COM creates the class factory. With this simple framework provided in this article, you can implement very basic COM components, such as shell extensions (shell Extensions). If you find any problems during use, please feedback it to vckbase@public.hk.hi.cn.

Here are the steps you can take to write your own COM objects in the way that this article says:

The first step: Write a header file that contains the following contents:

1, include file comdef.h: #include.

2, define the GUID of the COM server.

_declspec(selectany) GUID CLSID_Mine = { 0xdc186800,
　　　　　0x657f,
　　　　　0x11d4,
　　　　　{0xb0, 0xb5,　0x0,　0x50,　0xba,　0xbf,　0xc9,　0x4}
　　　　};

3. Gives the IID of the interface and the definition of the method to be implemented by this interface. The method by which the client will use the IID and interface of this interface.

interface __declspec(uuid("F614FB00-6702-11d4-B0B7-0050BABFC904")) ImyInterface : public IUnknown
{
　　STDMETHOD(Square)(long *pVal)PURE;
　　STDMETHOD(Cube)(long *pVal)PURE;
};
客户端使用此接口：
HRESULT hr;
ImyInterface *pmine=(0);
hr = CoCreateInstance(CLSID_Mine,　　　　　　　 // COM 服务器的CLSID
　　　　　　　　　　　NULL,　　　　　　//不支持聚合
　　　　　　　　　　　CLSCTX_INPROC_SERVER,　　 // 是个DLL
　　　　　　　　　　　__uuidof(ImyInterface),　 // 接口的IID
　　　　　　　　　　　(void**)&pmine
　　　　　　　　　　　);

Another way to get the CLSID of a COM object from the registry is to call the CLSIDFromProgID () function, but you must pass the ProgID of the component to the function.

Step Two: You must provide an implementation for the interface you define, and this article uses the method to create a new class that inherits from the interface:

This class implements single interface IMyInterface ...

//

//

class CmyInterface : public CComBase<> ,
　　　　　　　　 public InterfaceImpl
{
public:
　　CmyInterface();
　　virtual ~CmyInterface();
　　// 我们必须要为QueryInterface 编写代码
　　STDMETHOD(QueryInterface)(REFIID riid,LPVOID *ppv);
　　// ImyInterface 接口方法
　　STDMETHOD(Square)(long *pVal);
　　STDMETHOD(Cube)(long *pVal);
};

The template class interfaceimpl<> provides an implementation of the interface reference count. Here we can inherit from multiple interfaces, so that we can implement multiple interfaces in a COM component.