Typedef, Enum, Union, and Struct Attributes
The latest version of this topic can be found at Typedef, Enum, Union, and Struct Attributes.
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. |