switch-type.md

description	title	ms.date	f1_keywords	helpviewer_keywords	ms.assetid
Learn more about: switch_type	switch_type (C++ COM Attribute)	10/02/2018	vc-attr.switch_type	switch_type attribute	e24544dc-b3bc-48ae-b249-f967db49271e

switch_type

Identifies the type of the variable used as the union discriminant.

Syntax

[switch_type(
type
}]

Parameters

type
The switch type, can be an integer, character, Boolean, or enumeration type.

Remarks

The switch_type C++ attribute has the same functionality as the switch_type MIDL attribute.

C++ attributes do not support encapsulated unions. Nonencapsulated unions are supported only in the following form:

// cpp_attr_ref_switch_type.cpp
// compile with: /LD
#include <windows.h>
[module(name="MyLibrary")];
[ export ]
struct SizedValue2 {
   [switch_type("char"), switch_is(kind)] union {
      [case(1), string]
         wchar_t* wval;
      [default, string]
         char* val;
   };
   char kind;
};

Example

See the case example for a sample use of switch_type.

Requirements

Attribute context	Value
Applies to	typedef
Repeatable	No
Required attributes	None
Invalid attributes	None

For more information about the attribute contexts, see Attribute Contexts.

See also

IDL Attributes
Typedef, Enum, Union, and Struct Attributes
export