The document discusses the evolution of Ruby object-mapping libraries, starting from DataMapper in 2010 to the renaming to rom-rb in 2013. It highlights features and improvements in different versions, such as advanced querying and custom data types, culminating in the upcoming rom 2.0 with enhanced schemas and command support. Additionally, it introduces the dry-rb ecosystem, which provides low-level building blocks and high-level abstractions for managing dependencies and validation in Ruby applications.

1. MEET ROM-RB & DRY-RB
PIOTR SOLNICA

2. HI PIVORAK!
I’M SOLNIC :)

3. mojotech.com
rom-rb.org dry-rb.org

4. THE STORY

5. DATAMAPPER
2010

6. DATAMAPPER
▸ Active Record ORM with explicit model property
definitions
▸ Advanced query API in 2009 already (lazy queries, lazy
properties, advanced query operators etc.)
▸ Custom data types for properties
▸ Database-agnostic through adapters

7. VIRTUS
2011

8. VIRTUS
▸ Typed attribute definitions in PORO extracted from
DataMapper
▸ Advanced coercion mechanism
▸ Fully configurable and flexible
▸ Form objects, data objects (ie loaded from JSON),
coercion backends etc.
▸ For some reason people loved it…

9. DATAMAPPER 2
2012

10. DATAMAPPER 2
▸ Active Record => Data Mapper (patterns)
▸ Adapters based on pure relational algebra backend
▸ Advanced Session with Unit of Work for state tracking and
data synchronization
▸ Didn’t really work out ¯_(⊙_ʖ⊙)_/¯
▸ However…

11. EXPERIMENTATION BEHIND
DM2 HAS BEEN FRUITFUL!

12. RESULTS OF THE DATAMAPPER 2 EXPERIMENT
▸ Immutability-oriented object design!
▸ Focus on simpler, foundational abstractions
▸ Embracing small, composable libraries
▸ Lots of interesting new patterns in Ruby

13. ROM-RB
2013->2014

14. ROM-RB 2013->2014
▸ DataMapper 2 renamed to rom-rb (Ruby Object Mapper)
in 2013
▸ More work has been put into its relational algebra
backend and optimizing sql queries
▸ Prototype of Session with Unit of Work
▸ Still not production ready ¯_(⊙_ʖ⊙)_/¯

15. ( ಠ ಠ)

16. “ORM is one of the most complex things that you can ever touch…and we
chose it over and over again, without thinking at all, because everybody is
doing it”
Rich Hickey

17. ROM-RB
2014+

18. ROM-RB

19. PERSISTENCE & MAPPING
TOOLKIT FOR RUBY

20. NO COMPLEX
& LEAKY ABSTRACTIONS

21. REDUCES GLOBAL
STATE TO THE MINIMUM

22. FIGHTS WITH
MUTABLE STATE

23. MIXES FP WITH OO

24. CORE CONCEPTS
▸ Configuration
▸ Relations
▸ Pipelines
▸ Commands

25. CONFIGURATION

26. require 'rom'
config = ROM::Configuration.new(
:sql, 'postgres://localhost/rom_repository'
)
rom = ROM.container(config)
rom.gateways[:default]
# #<ROM::SQL::Gateway:0x007fde7a087158>

27. RELATIONS

28. class Users < ROM::Relation[:sql]
def sorted
order(:name)
end
end
JUST DATA
QUERY LOGIC
rom.relations[:users].sorted
# [{:id=>1, :name=>"Jane"}

29. RELATIONS ARE CALLABLE

30. rom.relations[:users].call
# [{:id=>1, :name=>"Jane"}]
rom.relations[:users].where(name: 'Jane').call
# [{:id=>1, :name=>"Jane"}]
rom.relations[:users].where(name: 'Joe').call
# []

31. PIPELINE

32. map_names = -> users { users.map { |user| user[:name] } }
user_names = rom.relations[:users] >> map_names
user_names.call
# ["Jane"]
PIPELINE OPERATOR

33. COMMANDS

34. class CreateUser < ROM::Commands::Create[:sql]
relation :users
register_as :create
result :one
end
create_user = rom.commands[:users][:create]
create_user.call(name: 'Joe')
# [{:id=>2, :name=>"Joe"}

35. ROM-REPOSITORY

36. class UserRepo < ROM::Repository
relations :users
def all
users.select(:name).to_a
end
end

37. user_repo = UserRepo.new(rom)
user_repo.all
# [#<ROM::Struct name="Jane">, #<ROM::Struct name="Joe">]

38. UPCOMING
COMMAND SUPPORT

39. class UserRepo < ROM::Repository[:users]
commands :create, update: :by_id
end
user = user_repo.create(name: "Jane", email: "jane@doe.org")
user_repo.update(user.id, name: "Jane Doe")

40. ROM 2.0 IS AROUND
THE CORNER!!!

41. ROM 2.0 + ROM-SQL + ROM-REPOSITORY UPDATES
▸ type-safe and flexible relation schema DSL
▸ association support in schemas
▸ simplified, automatic eager-loading based on association
definitions
▸ simplified interface for returning aggregate objects in
repositories
▸ support for persisting nested data into multiple relations

42. DRY-RB

44. ‣Low level building blocks
‣High-level abstractions

45. DRY-CONTAINER

46. LIGHTWEIGHT IOC

47. require 'dry-container'
class MyContainer
extend Dry::Container::Mixin
end
# register a singleton
MyContainer.register(:user_repo, UserRepo.new)
# or resolve as a new object
MyContainer.register(:user_repo) { UserRepo.new }
# simply access your registered objects
MyContainer[:user_repo]

48. class PersistUser
attr_reader :user_repo
def initialize(user_repo)
@user_repo = user_repo
end
def call(user)
user_repo.create(user)
end
end
PersistUser.new(MyContainer[:user_repo])

49. MyContainer.register(:persist_user) do
PersistUser.new(MyContainer[:user_repo])
end
MyContainer[:persist_user].call(user_data)

50. DRY-AUTO_INJECT

51. CONSTRUCTOR
INJECTION MIXIN

52. require 'dry-auto_inject'
Inject = Dry::AutoInject(MyContainer)

53. class PersistUser
include Inject[:user_repo]
def call(user)
user_repo.create(user)
end
end

54. MyContainer.register(:persist_user) do
PersistUser.new
end

55. DRY-COMPONENT

56. MANAGING STATE

57. require 'dry/component/container'
class Application < Dry::Component::Container
configure do |config|
config.root = Pathname.new('./my/app')
end
end
# now you can register a logger
require 'logger'
Application.register('utils.logger', Logger.new($stdout))
# and access it
Application['utils.logger']

58. AUTO-
REGISTRATION

59. require 'dry/component/container'
class Application < Dry::Component::Container
configure do |config|
config.root = '/my/app'
config.auto_register = 'lib'
end
load_paths!('lib')
end

60. # under /my/app/lib/logger.rb we put
class Logger
# some neat logger implementation
end
# we can finalize the container which triggers auto-registration
Application.finalize!
# the logger becomes available
Application[‘logger']

61. BOOTING
3RD-PARTY DEPS

62. Application.finalize(:persistence) do
require '3rd-party/database'
container.register('database') do
# some code which initializes this thing
end
end

63. class Application < Dry::Component::Container
configure do |config|
config.root = '/my/app'
end
end
# requires needed files and boots your persistence component
Application.boot!(:persistence)
# and now `database` becomes available
Application['database']

64. DRY-TYPES

65. A TYPE SYSTEM FOR RUBY
WITH COERCIONS AND
CONSTRAINTS

66. DRY-TYPES TURNS
RUBY INTO HASKELL

68. NOT REALLY :)

69. BUT TYPE-SAFETY
MATTERS

70. require 'dry-types'
module Types
include Dry::Types.module
end
Types::Coercible::String[1] # => "1"
Types::Form::Nil[""] # => nil
Types::Form::Float["1.23"] # 1.23

71. NilOrString = Types::Strict::Nil | Types::Strict::String
NilOrString[nil] # nil
NilOrString["foo"] # "foo"

72. DefaultAge = Types::Strict::Int.default(33)
DefaultAge[nil] # 33
Default[35] # 35
DefaultAge["35"]
# Dry::Types::ConstraintError: "35" violates constraints (type?
(Integer) failed)

73. UserAge = Types::Strict::Int.constrained(gt: 18)
UserAge[19]
# 19
UserAge[18]
# Dry::Types::ConstraintError: 17 violates constraints (gt?(18)
failed)

74. class User < Dry::Types::Struct
attribute :id, Types::Strict::Int
attribute :name, Types::Strict::String
end
User.new(id: 1, name: "Jane")

75. 0.8.0 IS AROUND
THE CORNER

76. DRY-VALIDATION

77. FAST, POWERFUL
VALIDATION WITH TYPE-
SAFETY & SAFE COERCIONS

78. VALIDATION
SCHEMAS

79. require 'dry-validation'
UserSchema = Dry::Validation.Schema do
required(:login).filled(:str?, size?: 2..64)
required(:age).maybe(:int?, gt?: 18)
end

80. UserSchema.(login: "j", age: 19).messages
# {:login=>["length must be within 2 - 64"]}
UserSchema.(login: "jane", age: nil).messages
# {}

81. SCHEMAS WITH
COERCIONS

82. require 'dry-validation'
UserSchema = Dry::Validation.Form do
required(:login).filled(:str?, size?: 2..64)
required(:age).maybe(:int?, gt?: 18)
end

83. UserSchema.(login: "jane", age: '19').to_h
# {:login=>"jane", :age=>19}
UserSchema.(login: "jane", age: '').to_h
# {:login=>"jane", :age=>nil}
UserSchema.(login: "j", age: '19').messages
# {:login=>["length must be within 2 - 64"]}
UserSchema.(login: "j", age: 'oops').messages
# {:age=>["must be an integer", "must be greater than 18"]}
UserSchema.(login: "jane", age: '').messages
# {}

84. UserSchema.(login: "j", age: 'oops').messages
# {:age=>["must be an integer", "must be greater than 18"]}
VALIDATION HINT
VALIDATION ERROR

85. 0.8.0 IS AROUND
THE CORNER

86. OMG MORE DRY-RB GEMS!
▸ dry-transaction
▸ dry-monads
▸ dry-initializer
▸ dry-web
▸ dry-web-roda (we plan to add support for more!)
▸ more gems are planned!

87. @rom_rb
rom-rb.org

88. dry-rb.org
@dry_rb

89. @_solnic_
solnic.eu
Piotr Solnica

90. dry-rb.org/resources/reddotrubyconf-2016/
More resources!

91. THANK YOU :)