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Typedef, Enum, Union, and Struct Attributes

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The following attributes apply to the typedef, struct, and enum C++ keywords.

typedef

Attribute Description
case Used with the switch_type attribute in a union.
custom Lets you define your own attribute.
export Causes a data structure to be placed in the .idl file.
first_is Specifies the index of the first array element to be transmitted.
helpcontext Specifies a context ID that lets the user view information about this element in the Help file.
helpfile Sets the name of the Help file for a type library.
helpstring Specifies a character string that is used to describe the element to which it applies.
library_block Places a construct inside the .idl file's library block.
ptr Designates a pointer as a full pointer.
public Ensures that a typedef will go into the type library even if it is not referenced from within the .idl file.
ref Identifies a reference pointer.
switch_is Specifies the expression or identifier acting as the union discriminant that selects the union member.
switch_type Identifies the type of the variable used as the union discriminant.
unique Specifies a unique pointer.
wire_marshal Specifies a data type that will be used for transmission instead of an application-specific data type.

enum

Attribute Description
custom Lets you define your own attribute.
export Causes a data structure to be placed in the .idl file.
uuid Specifies the unique ID for a class or interface.
v1_enum Directs that the specified enumerated type be transmitted as a 32-bit entity, rather than the 16-bit default.

union

Attribute Description
custom Lets you define your own attribute.
export Causes a data structure to be placed in the .idl file.
first_is Specifies the index of the first array element to be transmitted.
last_is Specifies the index of the last array element to be transmitted.
length_is Specifies the number of array elements to be transmitted.
max_is Designates the maximum value for a valid array index.
size_is Specifies the size of memory allocated for sized pointers, sized pointers to sized pointers, and single- or multidimensional arrays.
unique Specifies a unique pointer.
uuid Specifies the unique ID for a class or interface.

Nonencapsulated union

Attribute Description
ms_union Controls the network data representation alignment of nonencapsulated unions.
no_injected_text Prevents the compiler from injecting code as a result of attribute use.

struct

Attribute Description
aggregatable Indicates that the class supports aggregation.
aggregates Indicates that a control aggregates the target class.
appobject Identifies the coclass as an application object, which is associated with a full .exe application, and indicates that the functions and properties of the coclass are globally available in this type library.
coclass Creates an ActiveX control.
com_interface_entry Adds an interface entry to a COM map.
control Specifies that the user-defined type is a control.
custom Lets you define your own attribute.
db_column Binds a specified column to the rowset.
db_command Creates an OLE DB command.
db_param Associates the specified member variable with an input or output parameter and delimits the variable.
db_source Creates a connection to a data source.
db_table Opens an OLE DB table.
default Indicates that the custom or dispinterface defined within a coclass represents the default programmability interface.
defaultvtable Defines an interface as the default vtable interface for a control.
event_receiver Creates an event receiver.
event_source Creates an event source.
export Causes a data structure to be placed in the .idl file.
first_is Specifies the index of the first array element to be transmitted.
hidden Indicates that the item exists but should not be displayed in a user-oriented browser.
implements_category Specifies implemented component categories for the class.
last_is Specifies the index of the last array element to be transmitted.
length_is Specifies the number of array elements to be transmitted.
max_is Designates the maximum value for a valid array index.
requires_category Specifies the required component categories of the target class.
size_is Specifies the size of memory allocated for sized pointers, sized pointers to sized pointers, and single- or multidimensional arrays.
source On a class, specifies the COM object's source interfaces for connection points. On a property or method, indicates that the member returns an object or VARIANT that is a source of events.
threading Specifies the threading model for a COM object.
unique Specifies a unique pointer.
uuid Specifies the unique ID for a class or interface.
version Identifies a particular version among multiple versions of a class.
vi_progid Specifies a version-independent form of the ProgID.

See also

Attributes by Usage