optional (C++)
The latest version of this topic can be found at optional (C++).
Specifies an optional parameter for a member function.
Syntax
[optional]
Remarks
The optional C++ attribute has the same functionality as the optional MIDL attribute.
Example
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);
};
Requirements
Attribute Context
| Applies to | Interface parameter |
| Repeatable | No |
| Required attributes | None |
| Invalid attributes | None |
For more information about the attribute contexts, see Attribute Contexts.