Use QueryInterface Example (C++ COM)

This example shows how to use QueryInterface.

LPUNKNOWN iUnk = NULL;

LPFEATURE m_Feature = NULL;

HRESULT hres = S_FALSE;

// Your code

...

// Get the underlying object

hres = m_Feature->IGetSpecificFeature( &iUnk );  

LPREFPLANE m_RefPlane = NULL;

hres = iUnk->QueryInterface( IID_IRefPlane, (LPVOID*)&m_RefPlane);

// If Feature is a RefPlane

if (hres == S_OK && m_RefPlane != NULL)   

{

AfxMessageBox( _T("This feature is a reference plane") );

// Use m_RefPlane object

...

// Release m_RefPlane object

m_RefPlane->Release();     

}

// Release iUnk object

iUnk->Release();       

/*

   The call to IGetSpecificFeature increases the reference count on iUnk by 1. If the call to QueryInterface is successful, it also increases the reference count on iUnk by 1. The m_RefPlane and iUnk pointers are the same object; you can therefore release either one. m_RefPlane->Release() is shown in this example.

*/