TDC 2014 - Combata a obesidade: Técnicas para thin models

Ao iniciamos nossa jornada com o Rails, lemos o guides, alguns blog posts e começamos a nos divertir. Porém, após caminharmos um pouco seguindo as old conventions que ficaram enraizadas na cultura do framework, acabamos deixando de lado conceitos básicos que ajudam na sanidade e manutenabilidade de nossa
codebase por comodidade.

Quando vemos nossos projetos crescerem, toda a diversão do início se torna um peso. Para que ninguém culpe o framework, quero mostrar que existem maneiras de desenvolvermos nossas aplicações desde o início seguindo práticas que vão suportar aplicações de porte médio e grande.

Veremos como escrever models enxutos e de única responsabilidade, passando toda a gordura de validações, callbacks, nested_attributes e regras de negócios complexas, queries complexas e etc para quem realmente deve tratar disso.

Referências:
http://blog.codeclimate.com/blog/2012/10/17/7-ways-to-decompose-fat-activerecord-models/
http://blog.sensible.io/2014/04/19/don-t-just-dump-code-into-your-models.html

Transcript

1. Combata  a  obesidade Técnicas  para  thin  models
2. Carlos  Eduardo  L.  Lopes github.com/carloslopes   twitter.com/_carloslopes   speakerdeck.com/carloslopes
4. Projects ~>
5. rails new nice_app Projects ~>
6. create create README.rdoc create Rakefile create config.ru create .gitignore create Gemfile create app create app/assets/javascripts/application.js create app/assets/stylesheets/application.css create app/controllers/application_controller.rb create app/helpers/application_helper.rb create app/views/layouts/application.html.erb create app/assets/images/.keep create app/mailers/.keep create app/models/.keep create app/controllers/concerns/.keep create app/models/concerns/.keep create bin create bin/bundle create bin/rails create bin/rake create config create config/routes.rb rails new nice_app Projects ~>
7. Rails  -­‐>  MVC
8. Model View Controller Persistência Orquestrador HTMLs
9. Model View Controller Router ???
10. Model View Controller Router 1 2 3
11. Model View Controller Router 1 4 5 2 3
12. Model  -­‐>  Persistência
13. Model Validações   Callbacks   Regras  de  negócio   Queries  complexas   Regras  de  apresentação   Relacionamento   Persistência
14. Model Validações   Callbacks   Regras  de  negócio   Queries  complexas   Regras  de  apresentação   Relacionamento   Persistência Fat Models
15. class User < ActiveRecord::Base
 end
16. class User < ActiveRecord::Base
 validates :email, presence: true, 
 email: true
 validates :secondary_email, allow_blank: true, 
 email: true
 validates :name, presence: true
 validates :cpf, presence: true, 
 format: %r(\A\d+\z)
 validates :birth_date, presence: true
 end
17. class User < ActiveRecord::Base
 validates :email, presence: true, 
 email: true
 validates :secondary_email, allow_blank: true, 
 email: true
 validates :name, presence: true
 validates :cpf, presence: true, 
 format: %r(\A\d+\z)
 validates :birth_date, presence: true
 
 has_one :address
 end
18. class User < ActiveRecord::Base
 validates :email, presence: true, 
 email: true
 validates :secondary_email, allow_blank: true, 
 email: true
 validates :name, presence: true
 validates :cpf, presence: true, 
 format: %r(\A\d+\z)
 validates :birth_date, presence: true
 
 has_one :address
 
 accept_nested_attributes_for :address
 end
19. class User < ActiveRecord::Base
 validates :email, presence: true, 
 email: true
 validates :secondary_email, allow_blank: true, 
 email: true
 validates :name, presence: true
 validates :cpf, presence: true, 
 format: %r(\A\d+\z)
 validates :birth_date, presence: true
 
 has_one :address
 
 accept_nested_attributes_for :address
 
 after_destroy :remove_picture
 
 private
 def remove_picture
 # Code to remove profile picture
 end
 end
20. class User < ActiveRecord::Base
 validates :email, presence: true, 
 email: true
 validates :secondary_email, allow_blank: true, 
 email: true
 validates :name, presence: true
 validates :cpf, presence: true, 
 format: %r(\A\d+\z)
 validates :birth_date, presence: true
 
 has_one :address
 has_many :orders
 
 accept_nested_attributes_for :address
 
 after_destroy :remove_picture
 
 def special?
 last_login_at > 15.days.ago &&
 orders.last.created_at > 5.days.ago
 end
 
 private
 def remove_picture
 # Code to remove profile picture
 end

21. accept_nested_attributes_for :address
 
 after_destroy :remove_picture
 
 def special?
 last_login_at > 15.days.ago &&
 orders.last.created_at > 5.days.ago
 end
 
 def formatted_name
 if gender == 'male'
 "Derp #{name}"
 else
 "Derpina #{name}"
 end
 end
 
 def formatted_birth_date
 I18n.l(birth_date, format: :short)
 end
 
 private
 def remove_picture
 # Code to remove profile picture
 end
 end
22. if gender == 'male'
 "Derp #{name}"
 else
 "Derpina #{name}"
 end
 end
 
 def formatted_birth_date
 I18n.l(birth_date, format: :short)
 end
 
 def self.apple_buyers
 apple_orders = Order.where(provider: 'Apple')
 where(id: apple_orders.select(:user_id))
 end
 
 private
 def remove_picture
 # Code to remove profile picture
 end
 end
23. class User < ActiveRecord::Base
 validates :email, presence: true, 
 email: true
 validates :secondary_email, allow_blank: true,
 email: true
 validates :name, presence: true
 validates :cpf, presence: true,
 format: %r(\A\d+\z)
 validates :birth_date, presence: true
 
 has_one :address
 has_many :orders
 
 accept_nested_attributes_for :address
 
 after_destroy :remove_picture
 
 def special?
 last_login_at > 15.days.ago &&
 orders.last.created_at > 5.days.ago
 end
 
 def formatted_name
 if gender == 'male'
 "Derp #{name}"
 else
 "Derpina #{name}"
 end
 end
 
 def formatted_birth_date
 I18n.l(birth_date, format: :short)
 end
 
 def self.apple_buyers
 apple_orders = Order.where(provider: 'Apple')
 where(id: apple_orders.select(:user_id))
 end
 
 private
 def remove_picture
 # Code to remove profile picture
 end
 end
24. \ Soluções?
25. \ Concerns
26. \ Orientação  a  objeto
27. Form  objects Validações  (+  nested  attributes)
28. class SignupForm
 include Virtus
 include ActiveModel::Model
 
 attr_reader :user, :address
 
 attribute :name, String
 # other attributes ...
 
 validates :email, presence: true
 # other validations
 
 def persisted?; false; end
 
 def save
 if valid?; persist!; true; else; false; end
 end
 
 private
 def persist!
 @user = User.create!(name: name ...)
 @address = @user.create_address!(street: street ...)
 end
 end

29. # Antes
 def create
 @user = User.new(params[:user]) # Rails 3+
 @user = User.new(user_params) # Rails 4+ 
 if @user.save
 # Success
 else
 # Error
 end
 end
 
 # Depois
 def create
 @form = SignupForm.new(params[:signup_form])
 
 if @form.save
 # Success
 else
 # Error
 end
 end
30. # Antes
 def create
 @user = User.new(params[:user]) # Rails 3+
 @user = User.new(user_params) # Rails 4+ 
 if @user.save
 # Success
 else
 # Error
 end
 end
 
 # Depois
 def create
 @form = SignupForm.new(params[:signup_form])
 
 if @form.save
 # Success
 else
 # Error
 end
 end
31. class User < ActiveRecord::Base
 validates :email, presence: true, 
 email: true
 validates :secondary_email, allow_blank: true,
 email: true
 validates :name, presence: true
 validates :cpf, presence: true,
 format: %r(\A\d+\z)
 validates :birth_date, presence: true
 
 has_one :address
 has_many :orders
 
 accept_nested_attributes_for :address
 
 after_destroy :remove_picture
 
 def special?
 last_login_at > 15.days.ago &&
 orders.last.created_at > 5.days.ago
 end
 
 def formatted_name
 if gender == 'male'
 "Derp #{name}"
 else
 "Derpina #{name}"
 end
 end
 
 def formatted_birth_date
 I18n.l(birth_date, format: :short)
 end
 
 def self.apple_buyers
 apple_orders = Order.where(provider: 'Apple')
 where(id: apple_orders.select(:user_id))
 end
 
 private
 def remove_picture
 # Code to remove profile picture
 end
 end
32. Gems  para  form  objects Reform   activeform-­‐rails
33. Forms Validações Model Callbacks   Regras  de  negócio   Queries  complexas   Regras  de  apresentação   Relacionamento   Persistência
34. Service  objects Callbacks
35. class UserDestroyer
 def initialize(user)
 @user = user
 end
 
 def remove
 # Code to remove profile picture
 @user.destroy
 end
 end

36. # Antes
 def destroy
 @user = User.find(params[:id])
 @user.destroy
 redirect_to users_path
 end
 
 # Depois
 def destroy
 @user = User.find(params[:id])
 UserDestroyer.new(@user).destroy
 redirect_to users_path
 end
37. # Antes
 def destroy
 @user = User.find(params[:id])
 @user.destroy
 redirect_to users_path
 end
 
 # Depois
 def destroy
 @user = User.find(params[:id])
 UserDestroyer.new(@user).destroy
 redirect_to users_path
 end
38. class User < ActiveRecord::Base
 has_one :address
 has_many :orders
 
 after_destroy :remove_picture
 
 def special?
 last_login_at > 15.days.ago &&
 orders.last.created_at > 5.days.ago
 end
 
 def formatted_name
 if gender == 'male'
 "Derp #{name}"
 else
 "Derpina #{name}"
 end
 end
 
 def formatted_birth_date
 I18n.l(birth_date, format: :short)
 end
 
 def self.apple_buyers
 apple_orders = Order.where(provider: 'Apple')
 where(id: apple_orders.select(:user_id))
 end
 
 private
 def remove_picture
 # Code to remove profile picture
 end
 end
39. Gems  para  service  objects N/A
40. Model Regras  de  negócio   Queries  complexas   Regras  de  apresentação   Relacionamento   Persistência Services Callbacks Forms Validações
41. Policy  objects Regras  de  negócio
42. class SpecialUserPolicy
 def initialize(user)
 @user = user
 end
 
 def special?
 @user.last_login_at > 15.days.ago &&
 @user.orders.last > 5.days.ago
 end
 end
43. # Controller antes
 def index
 end # Controller depois
 def index
 @special_user_policy = SpecialUserPolicy.new(current_user)
 end <%# View antes %>
 <% if current_user.special? %>
 <% end %> <%# View depois %>
 <% if @special_user_policy.special? %>
 <% end %>
44. # Controller antes
 def index
 end # Controller depois
 def index
 @special_user_policy = SpecialUserPolicy.new(current_user)
 end <%# View antes %>
 <% if current_user.special? %>
 <% end %> <%# View depois %>
 <% if @special_user_policy.special? %>
 <% end %>
45. class User < ActiveRecord::Base
 has_one :address
 has_many :orders
 
 def special?
 last_login_at > 15.days.ago &&
 orders.last.created_at > 5.days.ago
 end
 
 def formatted_name
 if gender == 'male'
 "Derp #{name}"
 else
 "Derpina #{name}"
 end
 end
 
 def formatted_birth_date
 I18n.l(birth_date, format: :short)
 end
 
 def self.apple_buyers
 apple_orders = Order.where(provider: 'Apple')
 where(id: apple_orders.select(:user_id))
 end
 end
46. Gems  para  policy  objects N/A
47. Model Queries  complexas   Regras  de  apresentação   Relacionamento   Persistência Services Callbacks Forms Validações Policies Regras  de  negócio
48. Query  objects Queries  complexas
49. class AppleBuyers
 def initialize(relation = User.scoped)
 @relation = relation
 end
 
 def find_each(&block)
 @relation.
 where(id: apple_orders.select(:user_id)).
 find_each(&block)
 end
 
 private
 def apple_orders
 Order.where(provider: 'Apple')
 end
 end
50. # Antes
 def send
 User.apple_buyers.find_each do |user|
 MarketingMailer.apple_email(user).deliver
 end
 end
 
 # Depois
 def send
 AppleBuyers.new.find_each do |user|
 MarketingMailer.apple_email(user).deliver
 end
 end
51. # Antes
 def send
 User.apple_buyers.find_each do |user|
 MarketingMailer.apple_email(user).deliver
 end
 end
 
 # Depois
 def send
 AppleBuyers.new.find_each do |user|
 MarketingMailer.apple_email(user).deliver
 end
 end
52. class User < ActiveRecord::Base
 has_one :address
 has_many :orders
 
 def formatted_name
 if gender == 'male'
 "Derp #{name}"
 else
 "Derpina #{name}"
 end
 end
 
 def formatted_birth_date
 I18n.l(birth_date, format: :short)
 end
 
 def self.apple_buyers
 apple_orders = Order.where(provider: 'Apple')
 where(id: apple_orders.select(:user_id))
 end
 end
53. Gems  para  query  objects N/A
54. Model Regras  de  apresentação   Relacionamento   Persistência Services Callbacks Forms Validações Policies Regras  de  negócio Queries Queries  complexas
55. (Model)  Decorators Regras  de  apresentação
56. class UserDecorator < SimpleDelegator
 def initialize(user)
 @user = user
 super(user)
 end
 
 def name
 if gender == 'male'
 "Derp #{user.name}"
 else
 "Derpina #{user.name}"
 end
 end
 
 def birth_date
 h.l(user.birth_date, format: :short)
 end
 
 private
 attr_reader :user
 end
57. # Antes
 def show
 @user = User.find(params[:id])
 end
 
 # Depois
 def show
 @user = User.find(params[:id])
 @decorated_user = UserDecorator.new(@user)
 end
58. # Antes
 def show
 @user = User.find(params[:id])
 end
 
 # Depois
 def show
 @user = User.find(params[:id])
 @decorated_user = UserDecorator.new(@user)
 end
59. class User < ActiveRecord::Base
 has_one :address
 has_many :orders
 
 def formatted_name
 if gender == 'male'
 "Derp #{name}"
 else
 "Derpina #{name}"
 end
 end
 
 def formatted_birth_date
 I18n.l(birth_date, format: :short)
 end
 end
60. Gems  para  decorators Draper
61. Decorator  ou  Presenter?
62. Model Relacionamento   Persistência Services Callbacks Forms Validações Policies Regras  de  negócio Queries Queries  complexas Decorators Regras  de  apresentação
63. Considerações  finais
64. Model Validações   Callbacks   Regras  de  negócio   Queries  complexas   Regras  de  apresentação   Relacionamento   Persistência
65. Model Relacionamento   Persistência Services Callbacks Forms Validações Policies Regras  de  negócio Queries Queries  complexas Decorators Regras  de  apresentação
66. www.sandimetz.com www.poodr.com
67. devblog.avdi.org objectsonrails.com
68. Blogs http://robots.thoughtbot.com/   http://blog.codeclimate.com/blog/
69. Obrigado! @_carloslopes   Carlos  Eduardo  L.  Lopes