| title |
optional (C++ COM Attribute) | Microsoft Docs |
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| ms.date |
10/02/2018 |
| ms.technology |
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| ms.topic |
reference |
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| ms.assetid |
86656a66-8e11-4589-8e30-9b0f34eeed03 |
| author |
mikeblome |
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mblome |
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Specifies an optional parameter for a member function.
Remarks
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);
};
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| Applies to |
Interface parameter |
| Repeatable |
No |
| Required attributes |
None |
| Invalid attributes |
None |
For more information about the attribute contexts, see Attribute Contexts.
IDL Attributes
Parameter Attributes