# struct UUID

- UUID
- Struct
- Value
- Object

##
Overview

Represents a UUID (Universally Unique IDentifier).

NOTE To use `UUID`, you must explicitly import it with `require "uuid"`

##
Included Modules

- Comparable(UUID)

##
Defined in:

uuid.cr
uuid/json.cr

##
Constructors

- .empty : self

  Generates an empty UUID.

- .new(bytes : StaticArray(UInt8, 16), variant : UUID::Variant | Nil = nil, version : UUID::Version | Nil = nil)

  Generates UUID from bytes, applying version and variant to the UUID if present.

- .new(slice : Slice(UInt8), variant : Variant | Nil = nil, version : Version | Nil = nil)

  Creates UUID from 16-bytes slice.

- .new(uuid : UUID, variant : Variant | Nil = nil, version : Version | Nil = nil)

  Creates another `UUID` which is a copy of uuid, but allows overriding variant or version.

- .new(value : String, variant : Variant | Nil = nil, version : Version | Nil = nil)

  Creates new UUID by decoding `value` string from hyphenated (ie `ba714f86-cac6-42c7-8956-bcf5105e1b81`), hexstring (ie `89370a4ab66440c8add39e06f2bb6af6`) or URN (ie `urn:uuid:3f9eaf9e-cdb0-45cc-8ecb-0e5b2bfb0c20`) format, raising an `ArgumentError` if the string does not match any of these formats.

- .new(pull : JSON::PullParser)

  Creates UUID from JSON using `JSON::PullParser`.

- .random(random : Random = Random::Secure, variant : Variant = :rfc4122, version : Version = :v4) : self

  Generates RFC 4122 v4 UUID.

- .v1(*, clock_seq : UInt16 | Nil = nil, node_id : MAC | Nil = nil) : self

  Generates RFC 4122 v1 UUID.

- .v2(domain : Domain, id : UInt32, node_id : MAC | Nil = nil) : self

  Generates RFC 4122 v2 UUID.

- .v3(name : String, namespace : UUID) : self

  Generates RFC 4122 v3 UUID using the `name` to generate the UUID, it can be a string of any size.

- .v4(random r : Random = Random::Secure) : self

  Generates RFC 4122 v4 UUID.

- .v5(name : String, namespace : UUID) : self

  Generates RFC 4122 v5 UUID using the `name` to generate the UUID, it can be a string of any size.

##
Class Method Summary

- .from_json_object_key?(key : String)

  Deserializes the given JSON key into a `UUID`.

- .parse?(value : String, variant : Variant | Nil = nil, version : Version | Nil = nil) : UUID | Nil

  Creates new UUID by decoding `value` string from hyphenated (ie `ba714f86-cac6-42c7-8956-bcf5105e1b81`), hexstring (ie `89370a4ab66440c8add39e06f2bb6af6`) or URN (ie `urn:uuid:3f9eaf9e-cdb0-45cc-8ecb-0e5b2bfb0c20`) format, returning `nil` if the string does not match any of these formats.

- .v3_dns(name : String)

  Generates RFC 4122 v3 UUID with the `Namespace::DNS`.

- .v3_oid(name : String)

  Generates RFC 4122 v3 UUID with the `Namespace::OID`.

- .v3_url(name : String)

  Generates RFC 4122 v3 UUID with the `Namespace::URL`.

- .v3_x500(name : String)

  Generates RFC 4122 v3 UUID with the `Namespace::X500`.

- .v5_dns(name : String)

  Generates RFC 4122 v5 UUID with the `Namespace::DNS`.

- .v5_oid(name : String)

  Generates RFC 4122 v5 UUID with the `Namespace::OID`.

- .v5_url(name : String)

  Generates RFC 4122 v5 UUID with the `Namespace::URL`.

- .v5_x500(name : String)

  Generates RFC 4122 v5 UUID with the `Namespace::X500`.

##
Instance Method Summary

- #<=>(other : UUID) : Int32

  The comparison operator.

- #==(other : self)
- #bytes : StaticArray(UInt8, 16)

  Returns the binary representation of the UUID.

- #hash(hasher)

  See `Object#hash(hasher)`

- #hexstring : String
- #inspect(io : IO) : Nil

  Convert to `String` in literal format.

- #to_json(json : JSON::Builder) : Nil

  Returns UUID as JSON value.

- #to_s(io : IO) : Nil

  Same as `#inspect(io)`.

- #to_unsafe

  Returns unsafe pointer to 16-bytes.

- #urn : String

  Returns a `String` that is a valid urn of self

- #v1!

  Returns `true` if UUID is a V1, raises `Error` otherwise.

- #v1?

  Returns `true` if UUID is a V1, `false` otherwise.

- #v2!

  Returns `true` if UUID is a V2, raises `Error` otherwise.

- #v2?

  Returns `true` if UUID is a V2, `false` otherwise.

- #v3!

  Returns `true` if UUID is a V3, raises `Error` otherwise.

- #v3?

  Returns `true` if UUID is a V3, `false` otherwise.

- #v4!

  Returns `true` if UUID is a V4, raises `Error` otherwise.

- #v4?

  Returns `true` if UUID is a V4, `false` otherwise.

- #v5!

  Returns `true` if UUID is a V5, raises `Error` otherwise.

- #v5?

  Returns `true` if UUID is a V5, `false` otherwise.

- #variant : UUID::Variant

  Returns UUID variant based on the RFC4122 format.

- #version : UUID::Version

  Returns version based on RFC4122 format.

### Instance methods inherited from module `Comparable(UUID)`

<(other : T) : Bool <, <=(other : T) <=, <=>(other : T) <=>, ==(other : T) ==, >(other : T) : Bool >, >=(other : T) >=, clamp(min, max)
clamp(range : Range) clamp

### Instance methods inherited from struct `Struct`

==(other) : Bool ==, hash(hasher) hash, inspect(io : IO) : Nil inspect, pretty_print(pp) : Nil pretty_print, to_s(io : IO) : Nil to_s

### Instance methods inherited from struct `Value`

==(other : JSON::Any)
==(other : YAML::Any)
==(other) ==, dup dup

### Instance methods inherited from class `Object`

! : Bool !, !=(other) !=, !~(other) !~, ==(other) ==, ===(other : JSON::Any)
===(other : YAML::Any)
===(other) ===, =~(other) =~, as(type : Class) as, as?(type : Class) as?, class class, dup dup, hash(hasher)
hash hash, in?(collection : Object) : Bool
in?(*values : Object) : Bool in?, inspect(io : IO) : Nil
inspect : String inspect, is_a?(type : Class) : Bool is_a?, itself itself, nil? : Bool nil?, not_nil!(message)
not_nil! not_nil!, pretty_inspect(width = 79, newline = "\n", indent = 0) : String pretty_inspect, pretty_print(pp : PrettyPrint) : Nil pretty_print, responds_to?(name : Symbol) : Bool responds_to?, tap(&) tap, to_json(io : IO) : Nil
to_json : String to_json, to_pretty_json(indent : String = " ") : String
to_pretty_json(io : IO, indent : String = " ") : Nil to_pretty_json, to_s(io : IO) : Nil
to_s : String to_s, to_yaml(io : IO) : Nil
to_yaml : String to_yaml, try(&) try, unsafe_as(type : T.class) forall T unsafe_as

### Class methods inherited from class `Object`

from_json(string_or_io, root : String)
from_json(string_or_io) from_json, from_yaml(string_or_io : String | IO) from_yaml

### Macros inherited from class `Object`

class_getter(*names, &block) class_getter, class_getter!(*names) class_getter!, class_getter?(*names, &block) class_getter?, class_property(*names, &block) class_property, class_property!(*names) class_property!, class_property?(*names, &block) class_property?, class_setter(*names) class_setter, def_clone def_clone, def_equals(*fields) def_equals, def_equals_and_hash(*fields) def_equals_and_hash, def_hash(*fields) def_hash, delegate(*methods, to object) delegate, forward_missing_to(delegate) forward_missing_to, getter(*names, &block) getter, getter!(*names) getter!, getter?(*names, &block) getter?, property(*names, &block) property, property!(*names) property!, property?(*names, &block) property?, setter(*names) setter

##
Constructor Detail

def self.empty : self #

Generates an empty UUID.

    UUID.empty # => UUID(00000000-0000-4000-0000-000000000000)

def self.new(bytes : StaticArray(UInt8, 16), variant : UUID::Variant | Nil = nil, version : UUID::Version | Nil = nil) #

Generates UUID from bytes, applying version and variant to the UUID if present.

def self.new(slice : Slice(UInt8), variant : Variant | Nil = nil, version : Version | Nil = nil) #

Creates UUID from 16-bytes slice. Raises if slice isn't 16 bytes long. See `#initialize` for variant and version.

def self.new(uuid : UUID, variant : Variant | Nil = nil, version : Version | Nil = nil) #

Creates another `UUID` which is a copy of uuid, but allows overriding variant or version.

def self.new(value : String, variant : Variant | Nil = nil, version : Version | Nil = nil) #

Creates new UUID by decoding `value` string from hyphenated (ie `ba714f86-cac6-42c7-8956-bcf5105e1b81`), hexstring (ie `89370a4ab66440c8add39e06f2bb6af6`) or URN (ie `urn:uuid:3f9eaf9e-cdb0-45cc-8ecb-0e5b2bfb0c20`) format, raising an `ArgumentError` if the string does not match any of these formats.

def self.new(pull : JSON::PullParser) #

Creates UUID from JSON using `JSON::PullParser`.

NOTE `require "uuid/json"` is required to opt-in to this feature.

    require "json"
    require "uuid"
    require "uuid/json"

    class Example
      include JSON::Serializable

      property id : UUID
    end

    example = Example.from_json(%({"id": "ba714f86-cac6-42c7-8956-bcf5105e1b81"}))
    example.id # => UUID(ba714f86-cac6-42c7-8956-bcf5105e1b81)

def self.random(random : Random = Random::Secure, variant : Variant = :rfc4122, version : Version = :v4) : self #

Generates RFC 4122 v4 UUID.

It is strongly recommended to use a cryptographically random source for random, such as `Random::Secure`.

def self.v1(*, clock_seq : UInt16 | Nil = nil, node_id : MAC | Nil = nil) : self #

Generates RFC 4122 v1 UUID.

The traditional method for generating a `node_id` involves using the machine’s MAC address. However, this approach is only effective if there is only one process running on the machine and if privacy is not a concern. In modern languages, the default is to prioritize security and privacy. Therefore, a pseudo-random `node_id` is generated as described in section 4.5 of the RFC.

The sequence number `clock_seq` is used to generate the UUID. This number should be monotonically increasing, with only 14 bits of the clock sequence being used effectively. The clock sequence should be stored in a stable location, such as a file. If it is not stored, a random value is used by default. If not provided the current time milliseconds are used. In case the traditional MAC address based approach should be taken the `node_id` can be provided. Otherwise secure random is used.

def self.v2(domain : Domain, id : UInt32, node_id : MAC | Nil = nil) : self #

Generates RFC 4122 v2 UUID.

Version 2 UUIDs are generated using the current time, the local machine’s MAC address, and the local user or group ID. However, they are not widely used due to their limitations. For a given domain/id pair, the same token may be returned for a duration of up to 7 minutes and 10 seconds.

The `id` depends on the `domain`, for the `Domain::Person` usually the local user id (uid) is used, for `Domain::Group` usually the local group id (gid) is used. In case the traditional MAC address based approach should be taken the `node_id` can be provided. Otherwise secure random is used.

def self.v3(name : String, namespace : UUID) : self #

Generates RFC 4122 v3 UUID using the `name` to generate the UUID, it can be a string of any size. The `namespace` specifies the type of the name, usually one of `Namespace`.

def self.v4(random r : Random = Random::Secure) : self #

Generates RFC 4122 v4 UUID.

It is strongly recommended to use a cryptographically random source for random, such as `Random::Secure`.

def self.v5(name : String, namespace : UUID) : self #

Generates RFC 4122 v5 UUID using the `name` to generate the UUID, it can be a string of any size. The `namespace` specifies the type of the name, usually one of `Namespace`.

##
Class Method Detail

def self.from_json_object_key?(key : String) #

Deserializes the given JSON key into a `UUID`.

NOTE `require "uuid/json"` is required to opt-in to this feature.

def self.parse?(value : String, variant : Variant | Nil = nil, version : Version | Nil = nil) : UUID | Nil #

Creates new UUID by decoding `value` string from hyphenated (ie `ba714f86-cac6-42c7-8956-bcf5105e1b81`), hexstring (ie `89370a4ab66440c8add39e06f2bb6af6`) or URN (ie `urn:uuid:3f9eaf9e-cdb0-45cc-8ecb-0e5b2bfb0c20`) format, returning `nil` if the string does not match any of these formats.

def self.v3_dns(name : String) #

Generates RFC 4122 v3 UUID with the `Namespace::DNS`.

- `name`: The name used to generate the UUID, it can be a string of any size.

def self.v3_oid(name : String) #

Generates RFC 4122 v3 UUID with the `Namespace::OID`.

- `name`: The name used to generate the UUID, it can be a string of any size.

def self.v3_url(name : String) #

Generates RFC 4122 v3 UUID with the `Namespace::URL`.

- `name`: The name used to generate the UUID, it can be a string of any size.

def self.v3_x500(name : String) #

Generates RFC 4122 v3 UUID with the `Namespace::X500`.

- `name`: The name used to generate the UUID, it can be a string of any size.

def self.v5_dns(name : String) #

Generates RFC 4122 v5 UUID with the `Namespace::DNS`.

- `name`: The name used to generate the UUID, it can be a string of any size.

def self.v5_oid(name : String) #

Generates RFC 4122 v5 UUID with the `Namespace::OID`.

- `name`: The name used to generate the UUID, it can be a string of any size.

def self.v5_url(name : String) #

Generates RFC 4122 v5 UUID with the `Namespace::URL`.

- `name`: The name used to generate the UUID, it can be a string of any size.

def self.v5_x500(name : String) #

Generates RFC 4122 v5 UUID with the `Namespace::X500`.

- `name`: The name used to generate the UUID, it can be a string of any size.

##
Instance Method Detail

def <=>(other : UUID) : Int32 #
Description copied from module Comparable(UUID)

The comparison operator. Returns `0` if the two objects are equal, a negative number if this object is considered less than other, a positive number if this object is considered greater than other, or `nil` if the two objects are not comparable.

Subclasses define this method to provide class-specific ordering.

The comparison operator is usually used to sort values:

    # Sort in a descending way:
    [3, 1, 2].sort { |x, y| y <=> x } # => [3, 2, 1]

    # Sort in an ascending way:
    [3, 1, 2].sort { |x, y| x <=> y } # => [1, 2, 3]

def ==(other : self) #
def bytes : StaticArray(UInt8, 16) #

Returns the binary representation of the UUID.

def hash(hasher) #
Description copied from struct Struct

See `Object#hash(hasher)`

def hexstring : String #
def inspect(io : IO) : Nil #

Convert to `String` in literal format.

def to_json(json : JSON::Builder) : Nil #

Returns UUID as JSON value.

NOTE `require "uuid/json"` is required to opt-in to this feature.

    uuid = UUID.new("87b3042b-9b9a-41b7-8b15-a93d3f17025e")
    uuid.to_json # => "\"87b3042b-9b9a-41b7-8b15-a93d3f17025e\""

def to_s(io : IO) : Nil #
Description copied from struct Struct

Same as `#inspect(io)`.

def to_unsafe #

Returns unsafe pointer to 16-bytes.

def urn : String #

Returns a `String` that is a valid urn of self

    require "uuid"

    uuid = UUID.empty
    uuid.urn # => "urn:uuid:00000000-0000-4000-0000-000000000000"
    uuid2 = UUID.new("c49fc136-9362-4414-81a5-9a7e0fcca0f1")
    uuid2.urn # => "urn:uuid:c49fc136-9362-4414-81a5-9a7e0fcca0f1"

def v1! #

Returns `true` if UUID is a V1, raises `Error` otherwise.

def v1? #

Returns `true` if UUID is a V1, `false` otherwise.

def v2! #

Returns `true` if UUID is a V2, raises `Error` otherwise.

def v2? #

Returns `true` if UUID is a V2, `false` otherwise.

def v3! #

Returns `true` if UUID is a V3, raises `Error` otherwise.

def v3? #

Returns `true` if UUID is a V3, `false` otherwise.

def v4! #

Returns `true` if UUID is a V4, raises `Error` otherwise.

def v4? #

Returns `true` if UUID is a V4, `false` otherwise.

def v5! #

Returns `true` if UUID is a V5, raises `Error` otherwise.

def v5? #

Returns `true` if UUID is a V5, `false` otherwise.

def variant : UUID::Variant #

Returns UUID variant based on the RFC4122 format. See also `#version`

    require "uuid"

    UUID.new(Slice.new(16, 0_u8), variant: UUID::Variant::NCS).variant       # => UUID::Variant::NCS
    UUID.new(Slice.new(16, 0_u8), variant: UUID::Variant::RFC4122).variant   # => UUID::Variant::RFC4122
    UUID.new(Slice.new(16, 0_u8), variant: UUID::Variant::Microsoft).variant # => UUID::Variant::Microsoft
    UUID.new(Slice.new(16, 0_u8), variant: UUID::Variant::Future).variant    # => UUID::Variant::Future

def version : UUID::Version #

Returns version based on RFC4122 format. See also `#variant`.

    require "uuid"

    UUID.new(Slice.new(16, 0_u8), version: UUID::Version::V1).version # => UUID::Version::V1
    UUID.new(Slice.new(16, 0_u8), version: UUID::Version::V2).version # => UUID::Version::V2
    UUID.new(Slice.new(16, 0_u8), version: UUID::Version::V3).version # => UUID::Version::V3
    UUID.new(Slice.new(16, 0_u8), version: UUID::Version::V4).version # => UUID::Version::V4
    UUID.new(Slice.new(16, 0_u8), version: UUID::Version::V5).version # => UUID::Version::V5