Tools: HeaderDoc Unfettered: Tags for All Languages

## Tags for All Languages

#### In this section:

> Availability Macro Tags
> Constant Tags
> #define Tags
> Enum Tags
> Function Tags
> Function Group Tags
> Struct and Union Tags
> Typedef Tags
> Variable tags

### Availability Macro Tags

Tag | Identifies | Fields
--- | --- | ---
`@availabilitymacro` | The name of the availability macro and a string describing it. If the macro name appears in the declaration of any later function, class, method, or data type, the string will be added to its documentation as an availability attribute. See “Automatic Tagging” for more information. | 2

Listing 2-4 Example of @availabilitymacro tag

    /*!
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     @availabilitymacro AVAILABLE_IN_MYAPP_1_0_AND_LATER This function is available in version 1.0 and later of MYAPP.
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    */
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This is usually followed by a #define or similar, but that is not necessary. This HeaderDoc comment is a standalone comment—that is, it does not cause the code after it to be processed in any way. If you want to mark a `#define` as being an availability macro, you should follow this tag with a second HeaderDoc comment for the `#define` itself.

### Constant Tags

Tag | Identifies | Fields
--- | --- | ---
`@const` or `@constant` | Name of the constant. | 1

Listing 2-5 Example of @const tag

     /*!
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     @const kCFTypeArrayCallBacks
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     @discussion Predefined CFArrayCallBacks structure containing a set of callbacks appropriate...
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     */
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     const CFArrayCallBacks kCFTypeArrayCallBacks;
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### #define Tags

Tag | Identifies | Fields
--- | --- | ---
`@defined` | Name of the macro. | 1

Note: Function-like defines with curly braces may also use `@function`. This option is included for legacy compatibility and has no effect on the resulting output.

Listing 2-6 Example of @defined tag

     /*!
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     @defined TRUE
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     @discussion Defines the boolean true value.
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     */
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     #define TRUE 1
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For more usage examples, see the `ExampleHeaders` folder that accompanies the HeaderDoc distribution.

### Enum Tags

Tag | Identifies | Fields
--- | --- | ---
`@enum` | The name of the enumeration. This is the enum's tag, if it has one. Otherwise, supply a name you want to have the constants grouped under in the documentation. | 1
`@constant` | A constant within the enumeration. | 2

Listing 2-7 Example of @enum tag

    /*!
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     @enum Beverage Categories
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     @discussion Categorizes beverages into groups of similar types.
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     @constant kSoda Sweet, carbonated, non-alcoholic beverages.
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     @constant kBeer Light, grain-based, alcoholic beverages.
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     @constant kMilk Dairy beverages.
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     @constant kWater Unflavored, non-sweet, non-caloric, non-alcoholic beverages.
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    */
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    enum {
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     kSoda = (1 << 6),
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     kBeer = (1 << 7),
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     kMilk = (1 << 8),
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     kWater = (1 << 9)
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    }
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### Function Tags

Tag | Identifies | Fields
--- | --- | ---
`@function` | The name of the function or macro. | 1
`@param` | Each of the function's parameters. | 2
`@result` | The return value of the function. Don't include if the return value is void or OSERR | 1
`@throws` | Include one `@throws` tag for each exception thrown by this function (in languages that support exceptions). | 1
`@templatefield` | Each of the function’s template fields (C++). | 2

Listing 2-8 Example of @function tag

    /*!
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     @function ConstructBLT
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     @discussion Creates a Sandwich structure from the supplied arguments.
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     @param b Top ingredient, typically protein-rich.
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     @param l Middle ingredient.
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     @param t Bottom ingredient, controls tartness.
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     @param mayo A flag controlling addition of condiment. Use YES for condiment,
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     HOLDTHE otherwise.
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     @throws peanuts
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     @templatefield K The type of BLT to be generated (I want a BLT float)
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     @result A pointer to a Sandwich structure. Caller is responsible for
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     disposing of this structure.
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    */
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    Sandwich *ConstructBLT<K>(Ingredient b, Ingredient l, Ingredient t, Boolean mayo);
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### Function Group Tags

Tag | Identifies | Fields
--- | --- | ---
`@functiongroup` | The name of the function group. | 1

Listing 2-9 Example of @functiongroup tag

    /*!
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     @functiongroup Core Functions
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    */
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Function groups are not required, but they allow you to organize a large number of functions into near groupings. The `@functiongroup` tag remains in effect until the next `@functiongroup` tag.

If you need to put functions in different parts of the header into the same group, simply give them the same name (with the same capitalization, punctuation, spacing, etc.), and it will merge the two function groups into one.

Note that functions encountered before the first `@functiongroup` are considered part of the “empty” group. These functions will be listed before any grouped functions.

### Struct and Union Tags

Tag | Identifies | Fields
--- | --- | ---
`@struct` /`@union` | The name of the structure or union. (Also known as the struct or union's tag.) | 1
`@field` | A field in the structure. | 2

Listing 2-10 `Example of @struct` tag

    /*!
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     @struct TableOrigin
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     @discussion Locates lower-left corner of table in screen coordinates.
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     @field x Point on horizontal axis.
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     @field y Point on vertical axis
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    */
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    struct TableOrigin {
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     int x;
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     int y;
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    }
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### Typedef Tags

Tag | Identifies | Fields
--- | --- | ---
`@typedef` | The name of the defined type. | 1
various | The tags that can appear after a “`@typedef`” tag depend on the definition of the new type. `@field` for typedef’d structs `@constant` for typedef'd enumerations `@param` for simple typedef'd function pointers `@callback`, `@param`, `@result` for typedef'd structs containing function pointers |

Listing 2-11 Typedef for a simple struct

    /*!
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     @typedef TypedefdSimpleStruct
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     @abstract Abstract for this API.
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     @discussion Discussion that applies to the entire typedef'd simple struct.
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     @field firstField Description of first field
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     @field secondField Description of second field
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    */
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    typedef struct _structTag {
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     short firstField;
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     unsigned long secondField
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    } TypedefdSimpleStruct;
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Listing 2-12 Typedef for an enumeration

    /*!
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     @typedef TypedefdEnum
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     @abstract Abstract for this API.
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     @discussion Discussion that applies to the entire typedef'd enum.
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     @constant kCFCompareLessThan Description of first constant.
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     @constant kCFCompareEqualTo Description of second constant.
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     @constant kCFCompareGreaterThan Description of third constant.
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    */
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    typedef enum {
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     kCFCompareLessThan = -1,
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     kCFCompareEqualTo = 0,
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     kCFCompareGreaterThan = 1
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    } TypedefdEnum;
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Listing 2-13 Typedef for a simple function pointer

    /*!
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     @typedef simpleCallback
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     @abstract Abstract for this API.
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     @discussion Discussion that applies to the entire callback.
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     @param inFirstParameter Description of the callback's first parameter.
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     @param outSecondParameter Description of the callback's second parameter.
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     @result Returns what it can when it is possible to do so.
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    */
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    typedef long (*simpleCallback)(short inFirstParameter, unsigned long long *outSecondParameter);
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Listing 2-14 Typedef for a struct containing function pointers

    /*! @typedef TypedefdStructWithCallbacks
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     @abstract Abstract for this API.
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     @discussion Defines the basic interface for Command DescriptorBlock (CDB) commands.
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     @field firstField Description of first field.
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     @callback setPointers Specifies the location of the data buffer. The setPointers function has the following parameters:
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     @param cmd A pointer to the CDB command interface.
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     @param sgList A pointer to a scatter/gather list.
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     @result An IOReturn structure which returns the return value in the structure returned.
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     @field lastField Description of the struct's last field.
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    */
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    typedef struct _someTag {
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     short firstField;
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     IOReturn (*setPointers)(void *cmd, IOVirtualRange *sgList);
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     unsigned long lastField
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    } TypedefdStructWithCallbacks;
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### Variable tags

The `@var` tag should be used when marking up global variables, class variables, and instance variables (as opposed to actual declaration of new data types).

Tag | Identifies | Fields
--- | --- | ---
`@var` | The name of the data member followed by the description. | 2

Listing 2-15 Example of @var tag

    /*! @var we_are_root TRUE if this device is the root power domain */
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     boolwe_are_root;
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© 1999, 2004 Apple Computer, Inc. All Rights Reserved. (Last updated: 2004-05-27)