FAQ: 如何动态创建一个IDispatch接口

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问：如题

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2002年我曾经碰到过这个问题。

答：
为某个类的一个(目前只支持一个)虚函数动态的创建一个IDispatch接口
想知道更多的内容请在MSDN中查CreateStdDispatch


#define BEGIN_METHOD_PARAM() static LPPARAMDATA GetParamData(LPUINT pCount) { static PARAMDATA paras[] = {

#define METHOD_PARAM(NAME, TYPE) {OLESTR(#NAME), TYPE},

#define END_METHOD_PARAM() {NULL, VT_EMPTY} }; *pCount = sizeof(paras)/sizeof(paras[0])-1; return paras; };

template <class T, VARENUM TRET, int iMethod, CALLCONV cc = CC_STDCALL>
class ICallBackImpl : public IUnknown {
typedef ICallBackImpl<T, TRET, iMethod, cc> _Myt;
INTERFACEDATA InterfaceData;
METHODDATA MethodData;
IUnknown* punkStdDispatch;
LONG ref;
ICallBackImpl () : ref(0), punkStdDispatch(NULL) {
UINT count;
InterfaceData.pmethdata = &MethodData;
InterfaceData.cMembers = 1;
MethodData.szName = L"";
MethodData.ppdata = T::GetParamData(&count);
MethodData.dispid = DISPID_VALUE;
MethodData.iMeth = iMethod;
MethodData.cc = cc;
MethodData.cArgs = count;
MethodData.wFlags = DISPATCH_METHOD;
MethodData.vtReturn = TRET;
}
~ICallBackImpl() {
if(punkStdDispatch)
punkStdDispatch->Release();
}

public:
HRESULT STDMETHODCALLTYPE QueryInterface(REFIID riid, void** ppvObj) {
if(riid == IID_IUnknown) {
*ppvObj = this;
} else if(riid == IID_IDispatch) {
return punkStdDispatch->QueryInterface(riid, ppvObj);
} else
return E_NOINTERFACE;
AddRef();

return S_OK;
}
ULONG STDMETHODCALLTYPE AddRef() {
::InterlockedIncrement(&ref);
ods("++ %d\n", ref);
return ref;
}
ULONG STDMETHODCALLTYPE Release() {
ULONG prev = ::InterlockedDecrement(&ref);
if(ref == 0) {
ods("-- %d\n", 0);
delete this;
return 0;
}
ods("-- %d\n", ref);
return ref;
}
static HRESULT CreateInstance(T* pExposeObj, _Myt** pThis) {
HRESULT hr;
ITypeInfo* pTypeInfo;
if(IsBadWritePtr(pThis, sizeof(*pThis)))
return E_POINTER;
_Myt* pobj = new _Myt();
pobj->AddRef();
if(pobj == NULL)
return E_OUTOFMEMORY;
hr = ::CreateDispTypeInfo(&pobj->InterfaceData, LOCALE_SYSTEM_DEFAULT,
&pTypeInfo);
if(FAILED(hr))
goto error;
hr = ::CreateStdDispatch(pobj, pExposeObj, pTypeInfo,
&pobj->punkStdDispatch);
pTypeInfo->Release();
if(FAILED(hr))
goto error;
*pThis = pobj;
return S_OK;
error:
pobj->Release();
return hr;
}