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optional (C++)

Specifies an optional parameter for a member function.

[optional]

The optional C++ attribute has the same functionality as the optional MIDL attribute.

The following code shows how optional might be used:

// cpp_attr_ref_optional.cpp
// compile with: /LD
#include "unknwn.h"
[module(name="ATLFIRELib")];

[dispinterface, uuid("00000000-0000-0000-0000-000000000001")]
__interface IFireTabCtrl : IDispatch
{
   [id(1)] long procedure ([in, optional] VARIANT i);
};

Attribute Context

Applies to

Interface parameter

Repeatable

No

Required attributes

None

Invalid attributes

None

For more information about the attribute contexts, see Attribute Contexts.

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