| description | Learn more about: optional (C++) | |
|---|---|---|
| title | optional (C++ COM Attribute) | |
| ms.date | 10/02/2018 | |
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| ms.assetid | 86656a66-8e11-4589-8e30-9b0f34eeed03 |
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 | Value |
|---|---|
| Applies to | Interface parameter |
| Repeatable | No |
| Required attributes | None |
| Invalid attributes | None |
For more information about the attribute contexts, see Attribute Contexts.