COM

// IDL source for prj1.dll
//

// This file will be processed by the MIDL tool to
// produce the type library (prj1.tlb) and marshalling code.

import "oaidl.idl";
import "ocidl.idl";

[
	uuid(XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX), // GUID of your Type Library. Use GUIDGEN.EXE from MS Common\Tools
	version(n.m),                               // Version of your Type Library, e.g. 1.0 
	helpstring("XXXXXXXX")                      // Description of your Type Library
]
library XXXXLib                               // Name of your Type Library
{
	importlib("stdole32.tlb");
	importlib("stdole2.tlb");

typedef [
	uuid(XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX), // GUID of your Enum. Use GUIDGEN.EXE from MS Common\Tools
	version(n.m),                               // Version of your Enum, e.g. 1.0 
	helpstring("XXXXXXXX")                      // Description of your Enum
]
enum tagXXXX                                  // Name of your Enum
{
	[helpstring("XXXXXXXX")]                        // Description of your Enum Value
	XXXX = YYYY,                                    // Name and Value (optional as C++) of your Enum Value
//	and so on ...
} XXXX;                                       // Name of your Enum

typedef [
	uuid(XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX), // GUID of your Struct. Use GUIDGEN.EXE from MS Common\Tools
	version(n.m),                               // Version of your Struct, e.g. 1.0 
	helpstring("XXXXXXXX")                      // Description of your Struct
]
struct tagXXXX                                // Name of your Struct
{
  // your struct (as C++)
} XXXX;                                       // Name of your Struct

};

   typedef [uuid(XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX), helpstring("Help")] 
   struct _SomeStruct
   {
      int i;
      BSTR str;
...
   } SomeStruct;

   [...,dual,...]
   interface IO : IDispatch
   {
      [id(1)] HRESULT M1([in] SomeStruct ss);
      [id(2)] HRESULT M2([in,out] SomeStruct *ss);
      [id(3)] HRESULT M3([out,retval] SomeStruct* *ss);
      [id(4)] HRESULT M4([in,out] SAFEARRAY(SomeStruct) * ssbs);
   };

// CTeacher has a member: IStudent * m_student
// or it is better: CComPtr<IStudent> m_student

1. With the class factory of CStudent.
if( FAILED(CStudent::_CreatorClass::CreateInstance(NULL,IID_IStudent, (void**)&m_student)) )
	return E_FAIL;

2. With the static method of the generic ATL CComObject.
CComObject<CStudent>* pCStudent;
if( FAILED(pCStudent->CreateInstance(&pCStudent)) || FAILED(pCStudent->QueryInterface(&m_student)) )
	return E_FAIL;

3. With the original COM method.
if( FAILED(CoCreateInstance(CLSID_Student,NULL,CLSCTX_ALL,IID_IStudent, (void**)&m_student)) )
	return E_FAIL;

STDMETHODIMP CTeacher::get_OneStudent(IStudent **pVal)
{
   AFX_MANAGE_STATE(AfxGetStaticModuleState())

   // TODO: Add your implementation code here
   *pVal = m_aStudent;
   if (*pVal) {
      (*pVal)->AddRef();
   }
   return S_OK;
}