optional (C++)

  • Article

Specifies an optional parameter for a member function.

[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

Concepts

IDL Attributes

Parameter Attributes

ATL Samples