CODEWITHSUNDEEP
c++atl
lcs
lcs

Reputation: 4245

Override QueryInterface using ATL

Is it possible to provide an implementation to QueryInterface for classes using ATL?

BEGIN_COM_MAP(CConcrete) // Defines _InternalQueryInterface
  COM_INTERFACE_ENTRY(IInterface)
END_COM_MAP() // Defines QueryInterface as a pure virtual function which
              // is overridden in CComObject<CConcrete>

I'm overriding for mocking purposes, allowing a user to simulate a QueryInterface failure. I would like to maintain the default ATL QueryInterface functionality when not being explicitly configured.

The call stack looks like this:

CComObjectRootBase::InternalQueryInterface
CConcrete::_InternalQueryInterface // BEGIN_COM_MAP
CComObject<CConcrete>::QueryInterface // Override of QI from END_COM_MAP

Upvotes: 1

Views: 1033

Answers (1)

lcs
lcs

Reputation: 4245

What I ended up doing was creating a new version of BEGIN_COM_MAP that doesn't include an implementation for _InternalQueryInterface. I then put my mocking code in there, and forwarded non-mocked calls to InternalQueryInterface.

Upvotes: 1

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