Imutabilidade em ruby

Slides da apresentação: https://www.youtube.com/watch?v=2hioq6dohtI&t=2137s

1. Imutabilidade em Ruby

2. Bom dia! Maurício Szabo http://mauricio.szabo.link

3. Imutabilidade? Em Ruby? Por quê?

4. But Why!? Concorrencia Multi-thread Escalabilidade horizontal Blablabla... Previsibilidade Consistência Replicabilidade Composição Mantenabilidade

5. Previsibilidade

6. Consistência age = 18 age = 28 Person 1 Person 2 Task 1 Task 2 Task 3 Task 4

7. Replicabilidade f(10, 20, 30) 42

8. Replicabilidade f(10, 20, 30) 42

9. Replicabilidade rand() 0.01090 f(10, 20, 30)

10. Replicabilidade rand() 0.92100 f(10, 20, 30)

11. h Funções Puras rand f g h

12. Ruby, Finalmente Estruturas de Dados Imutáveis 1 https://bit.ly/2JjCUzE

13. Estruturas Hamster::Vector[] Hamster::Deque[] Hamster::List[] Hamster::Set[] Hamster::Hash[] Acesso via indice p ush / append p op / drop_last u nshift / prepend shift / tail

14. Performance? Spoiler: é mais lento!

15. Lista de Elementos (prepend) real Mutable array - unshift 0.050518 Mutable array - shift 0.028875 Immutable list - unshift 0.342788 (6.8x mais lento) Immutable list - shift 0.028016 (+/- mesma velocidade)

16. Lista de Elementos real Mutable array - push 0.047483 Mutable array - pop 0.029408 Mutable array - unshift 0.050518 Mutable array - shift 0.028875 Immutable deque - append at last 0.537605 (11x mais lento) Immutable deque - pop 0.179720 (6x mais lento) Immutable deque - append at first 0.496692 (9.5x mais lento) Immutable deque - shift 0.172747 (6x mais lento)

17. Random Access real Mutable array 0.047483 Mutable array - get random element 0.047016 Mutable array - pop 0.029408 Immutable vector 1.782584 (37x mais lento!!!) Immutable vector - get random element 0.213734 (4.5x mais lento) Immutable vector - pop 4.246951 (144x mais lento!!!)

18. “Hack” real Mutable array 0.343495 Immutable list - prepend 3.075296 (10x mais lento) Immutable list - from mutable 0.955190 (3.7x mais lento) Immutable Deque - from mutable 0.947304 (3.7x mais lento) Immutable Vector - from mutable 0.299589 (1.8x mais lento)

19. Objetos ! Trabalhando com instâncias imutáveis 🏈

20. An object has state (data) and behavior (code) (Wikipedia) Wikipedia is not a reliable source (Every university professor)

21. class User include Anima . new( :name , :email ) end user = User . new(name: "Foo" , email : "[email protected]" ) user . email << ".br" user . email # => "[email protected]" def user . nada "#{ name } = #{ email }" end user . nada # => "Foo = [email protected]" class User include Anima . new( :name , :email ) include Adamantium end user = User . new(name: "Foo" , email : "[email protected]" ) user . email << ".br" # => can’t modify frozen object def user . nada "#{ name } = #{ email }" e nd # => can’t modify frozen object

22. class User include Anima . new( :name , :email ) end user = User . new(name: "Foo" , email : "[email protected]" ) user2 = user.with( email : "[email protected]" ) user . email # => "[email protected]" user2 . email # => "[email protected]" Como trabalhar?

23. Padrões - Data First class User include Anima . new( :name , :children ) include UpInAnima NULL = new (name: "" , children : Hamster : :Vector [] ) end class Children include Anima . new( :name , :age ) include UpInAnima NULL = new (name: "" , age : ) end

24. Padrões - Data First https://bit.ly/2JjCUzE user = User : :NULL . with(name: "Ariovaldo" ) . update_in( :children ) { | c | c . add( Children : :NULL . with(name: "Emily" , age : 9 )) } # Emily's birthday! user . update_in( :children , , :age ) { | age | age + 1 }

25. Banco de Dados Datasets imutáveis, Sequel, ROM, ActiveRecord, etc...

26. Bancos de Dados id = 1 age = 9 id = 1 age = 10 Validate id = 1 age = 10

27. Either Monad Dados Dados Transformados Dados Transformados’ Erros Erros Erros UPDATE! Validate Dados para Update

28. Talk is Easy... class User extend Sequel : :Model :: ClassMethods include Anima . new( :id , :name , :email ) self . dataset = DB [ :users ] def self . call (param) new (param) end def update! (params) validate(params) . then do | new_obj | pk = self . class . primary_key pk_value = send(pk) self . class . dataset . where(pk => pk_value) . update(new_obj . to_h) new_obj end end private :with private def validate (params) new_obj = with(params) errors = NameValidation . call(new_obj . to_h) . errors if (errors . empty?) Either . right(new_obj) else Either . left(errors) end end end

29. class User extend Sequel : :Model :: ClassMethods include Anima . new( :id , :name , :email ) self . dataset = DB [ :users ] def self . call (param) new (param) end # ... end

30. class User # … private def validate (params) new_obj = with(params) errors = NameValidation . call(new_obj . to_h) . error if (errors . empty?) Either . right(new_obj) else Either . left(errors) end end end

31. class User # ... def update! (params) validate(params) . then do | new_obj | pk = self . class . primary_key pk_value = send(pk) s elf . class . dataset . where(pk => pk_value) . update(new_obj . to_h) new_obj end E nd private :with # ... end

32. u2 = u . update!(name: "" ) # => Either left=.... User . first # => #<User id=1 name="Foo Bar" email=nil> u2 = u . update!( email : "[email protected]" ) User . first # => #<User id=1 name="Foo Bar" email="[email protected]"> u2 = u . update!(name: "Szabo" ) User . first # => #<User id=1 name="Szabo" email=nil> u = User . first # => #<User id=1 name="Foo Bar" email=nil>

33. Transformação Imutável Dado FN Dado Alterado

34. []’s Perguntas? Meus links: http://mauricio.szabo.link [email protected] https://bit.ly/2JjCUzE