records — stdlib v8.0.2

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# records (stdlib v8.0.2)

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Native records processing functions.

This module contains functions for creating and inspecting native records.

#### Warning

The main purpose of the functions in this module is for debugging, implementing library functions (such as printing of native records), and implementing tools (such as the Debugger). Use with care in production code.

## Summary

### Types

create_options()

Options that can be used when creating a native record.

### Functions

create(Module, RecordName, Fields, Options)

Takes `Fields` and creates a native record `Record` with module `Module` and name `RecordName`.

get(Key, Record)

Returns value `Value` associated with `Key` if native record `Record` contains `Key`.

get_definition(Module, RecordName)

Retrieves the definition for native record `Name` in module `Module`.

get_field_names(Record)

Returns a complete list of field names (keys) in native record `Record`, in the order of declaration.

get_module(Record)

Returns the module `Module` in which the native record `Record` is defined.

get_name(Record)

Returns the name `Name` of the native record `Record`.

is_exported(Record)

Returns `true` if native record `Record` is exported; otherwise, returns `false`.

update(Src, Module, RecordName, FieldsMap)

Takes a map `FieldsMap` and updates the values in native record `Src` as defined in module `Module` with name `RecordName`.

## Types

# create_options()

(not exported) (since OTP 29.0)

    -type create_options() :: #{is_exported := boolean()}.

Options that can be used when creating a native record.

- The value for the `is_exported` key should be a boolean indicating whether this record value is exported.

Consumed by:

- `records:create/4`

## Functions

# create(Module, RecordName, Fields, Options)

(since OTP 29.0)

    -spec create(Module :: module(),
                 RecordName :: atom(),
                 Fields :: [{atom(), term()}],
                 Options :: create_options()) ->
                    record().

Takes `Fields` and creates a native record `Record` with module `Module` and name `RecordName`.

The native record definition does not have to exist in the given module, and if it exists, it will not be used in any way.

#### Warning

Because this function can create records that are inconsistent with the record definition in module `Module`, it can cause very subtle bugs; therefore, its use in applications is strongly discouraged.

The call can fail in the following ways:

- With a `{badrecord,Record}` exception if `Module` or `RecordName` are not atoms.
- With a `{badmap, OptionsMap}` exception if `OptionsMap` is not a map.
- With a `{badfield, Field}` exception if a field name in `Fields` is not an atom.
- With a `badarg` exception if `Options` does not have the `is_exported` key.
- With a `badarg` exception for other invalid arguments, such as a field name being repeated in `Fields`.

## Examples

    1> R = records:create(test, a, [{z,3}, {x,1}, {y,2}], #{is_exported => true}).
    #test:a{z = 3,x = 1,y = 2}
    2> records:is_exported(R).
    true
    3> records:create(test, a, [{42,1}], #{is_exported => true}).
    ** exception error: bad field name: 42 in #test:a{}
         in function  records:create/4
            called as records:create(test,a,[{42,1}],#{is_exported => true})
    4> records:create(test, a, [{x,1}, {x,2}], #{is_exported => true}).
    ** exception error: bad argument
         in function  records:create/4
            called as records:create(test,a,[{x,1},{x,2}],#{is_exported => true})

# get(Key, Record)

(since OTP 29.0)

    -spec get(Key, Record) -> dynamic() when Key :: atom(), Record :: record().

Returns value `Value` associated with `Key` if native record `Record` contains `Key`.

This call fails with a `badarg` exception if `Record` is not a native record or if `Key` does not exist in `Record`.

## Examples

    1> R = records:create(test, a, [{x,1}], #{is_exported=>false}).
    #test:a{x = 1}
    2> records:get(x, R).
    1
    3> records:get(y, R).
    ** exception error: bad argument
         in function  records:get/2
            called as records:get(y,#test:a{x = 1})

# get_definition(Module, RecordName)

(since OTP 29.0)

    -spec get_definition(Module :: module(), RecordName :: atom()) ->
                            {create_options(),
                             [{FieldName :: atom(), Default :: dynamic()} | (FieldName :: atom())]}.

Retrieves the definition for native record `Name` in module `Module`.

# get_field_names(Record)

(since OTP 29.0)

    -spec get_field_names(Record) -> [Name] when Record :: record(), Name :: atom().

Returns a complete list of field names (keys) in native record `Record`, in the order of declaration.

This call fails with a `{badrecord,Record}` exception if `Record` is not a native record.

## Examples

    1> R = records:create(test, a, [{x,1}], #{is_exported=>false}).
    #test:a{x = 1}
    2> records:get_field_names(R).
    [x]
    3> records:get_field_names({x,y}).
    ** exception error: {badrecord,{x,y}}
         in function  records:get_field_names/1
            called as records:get_field_names({x,y})

# get_module(Record)

(since OTP 29.0)

    -spec get_module(Record) -> Module when Record :: record(), Module :: module().

Returns the module `Module` in which the native record `Record` is defined.

This call fails with a `badarg` exception if `Record` is not a native record.

## Examples

    1> R = records:create(test, a, [{x,1}], #{is_exported=>false}).
    #test:a{x = 1}
    2> records:get_module(R).
    test
    3> records:get_module(#{}).
    ** exception error: bad argument
         in function  records:get_module/1
            called as records:get_module(#{})

# get_name(Record)

(since OTP 29.0)

    -spec get_name(Record) -> Name when Record :: record(), Name :: atom().

Returns the name `Name` of the native record `Record`.

This call fails with a `badarg` exception if `Record` is not a native record.

## Examples

    1> R = records:create(test, a, [{x,1}], #{is_exported=>false}).
    #test:a{x = 1}
    2> records:get_name(R).
    a
    3> records:get_name(#{}).
    ** exception error: bad argument
         in function  records:get_name/1
            called as records:get_name(#{})

# is_exported(Record)

(since OTP 29.0)

    -spec is_exported(record()) -> boolean().

Returns `true` if native record `Record` is exported; otherwise, returns `false`.

This call fails with a `{badrecord,Record}` exception if `Record` is not a native record.

## Examples

    1> R = records:create(test, a, [{x,1}], #{is_exported=>false}).
    #test:a{x = 1}
    2> records:is_exported(R).
    false
    3> records:is_exported({x,y}).
    ** exception error: {badrecord,{x,y}}
         in function  records:is_exported/1
            called as records:is_exported({x,y})

# update(Src, Module, RecordName, FieldsMap)

(since OTP 29.0)

    -spec update(Src :: record(),
                 Module :: module(),
                 RecordName :: atom(),
                 FieldsMap :: #{atom() => term()}) ->
                    record().

Takes a map `FieldsMap` and updates the values in native record `Src` as defined in module `Module` with name `RecordName`.

The call can fail in the following ways:

- With a `{badrecord,Record}` exception if `Src` is not a native record defined in module `Module` with name `RecordName`.
- With a `{badmap, FieldsMap}` if `FieldsMap` is not a map.
- With a `{badfield, Field}` if `Field` in `FieldsMap` does not exist in `Record`.

## Examples

    1> R = records:create(test, a, [{x,1}, {y,2}, {z,3}], #{is_exported => false}).
    #test:a{x = 1,y = 2,z = 3}
    2> Updated = records:update(R, test, a, #{x => 10, y => 20}).
    #test:a{x = 10,y = 20,z = 3}
    3> records:update(R, test, a, #{w => 42}).
    ** exception error: bad field name: w in #test:a{}
         in function  records:update/4
            called as records:update(#test:a{x = 1,y = 2,z = 3},test,a,#{w => 42})