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.

See also

IDL Attributes
Parameter Attributes