Rediscovering OOP in Rails World

A quick talk about application design, methods to improve your software. Evento Stack U, in Quito, Ecuador.

Transcript

1. REDISCOVERING OOP IN RAILS WORLD Filipe Costa @filipebarcos
2. Design
5. class Dealer < ActiveRecord::Base default_scope order('lower(name)') ! belongs_to :provider, conditions: { mobile: false } belongs_to :mobile_provider, class_name: 'Provider', conditions: { mobile: true } ! belongs_to :ftp_user, :dependent => :delete has_many :inventory_uploads, through: :ftp_user ! accepts_nested_attributes_for :ftp_user ! validates_associated :ftp_user ! has_many :inventories, :dependent => :delete_all ! before_destroy :purge_inventories ! has_many :error_log_entries ! # All cars (also from old inventory uploads) associated with this dealer. # Almost always you'll be interested in cars from most recent inventory via #recent_cars has_many :cars, through: :inventories ! belongs_to :autosocial_group ! has_many :performance_logs, :dependent => :delete_all, :class_name => 'CampaignPerformanceLog' ! has_many :dealer_ad_templates, order: "ad_template_type DESC", dependent: :destroy has_many :ad_templates, through: :dealer_ad_templates ! has_many :ad_groups, :dependent => :delete_all has_many :ads, :through => :ad_groups has_many :keywords, :through => :ad_groups has_many :group_negatives, :through => :ad_groups has_many :competitors, dependent: :destroy has_many :regions, dependent: :destroy has_many :dealer_makes, dependent: :destroy has_many :makes, through: :dealer_makes has_many :models, through: :dealer_makes has_one :dynamic_campaign, class_name: 'AdWordsCampaign', dependent: :destroy, conditions: { campaign_type: "Dynamic" } has_one :managed_campaign, class_name: 'AdWordsCampaign', dependent: :destroy, conditions: { campaign_type: "Managed" } has_many :ad_words_campaigns ! Is this familiar to you?
6. return if purging? update_attribute(:purge_queued_at, Time.now) Resque.enqueue(ProcessDealerPurge, self.id) end ! def enqueue_destroy return if deleted? update_attribute(:deleted, true) Resque.enqueue(ProcessDealerDestroy, self.id) end ! def purging? not purge_queued_at.nil? end ! def self.find_dealers(search_query) dealers = self.scoped dealers = dealers.merge(self.where('name ILIKE ?', "%#{search_query}%")) unless search_query.blank? dealers end ! def import_locations Haystack::AdWords::LocationsImporter.new(self).import end ! def google_campaign_id dynamic_campaign.try(:remote_campaign_id) end ! delegate :display_url, :destination_url, :mobile_bid_adjustment, :mobile_destination_url, to: :dynamic_campaign ! def models_titles_grouped_by_makes models.order(:title).each_with_object({}) do |model, result| result[model.make_title] ||= [] result[model.make_title] << model.title end end ! private ! def assign_templates Haystack::AdTemplates::Generator.new.assign_default_templates_for(self) end ! def adwords_account_missing? has_google_ads? && account_id.blank? end ! end Is this familiar to you?
7. That class is probably doing TOO MUCH
8. So what?
9. To help you with OOP, let’s check S.O.L.I.D principles
10. Let’s do this!
11. S O L I D
12. S O L I D ingle Responsibility
13. S O L I D ingle Responsibility pen/Closed
14. S O L I D ingle Responsibility pen/Closed iskov Substituition
15. S O L I D ingle Responsibility pen/Closed iskov Substituition nterface Segregation
16. S O L I D ingle Responsibility pen/Closed iskov Substituition nterface Segregation ependency Inversion
17. S O L I D ingle Responsibility pen/Closed iskov Substituition nterface Segregation ependency Inversion
18. Single Responsibility Principle (SRP)
20. class Invetory < ActiveRecord::Base def self.process file = download_file CSV.readlines(file) do |line| description, price = line self.create(description: description, price: price.to_d) end end ! private def download_file Net::HTTP.start("www.my-super-server.com") do |http| response = http.get("/path/to/file.csv") open("my-local-file.csv", "wb") do |file| file.write(response.body) end end end end
21. TOO MUCH
22. class Car < ActiveRecord::Base def self.process file = SuperDownloader.new.download_file CSV.foreach(file) do |line| description, price = line self.create(description: description, price: price) end end end ! class SuperDownloader def download_file # Download from interwebs end end !
23. Open/Close Principle (OCP)
24. OPEN for EXTENSION CLOSED for MODIFICATION
25. class Car < ActiveRecord::Base def self.process file = SuperDownloader.new.download_file CSV.foreach(file) do |line| description, price = line self.create(description: description, price: price) end end end ! class SuperDownloader def download_file # Download from interwebs end end !
26. What if I want to modify a little bit our downloader?
27. Dependency Injection
28. class Car < ActiveRecord::Base def self.process(downloader = SuperDownloader.new) file = downloader.download_file CSV.foreach(file) do |line| description, price = line self.create(description: description, price: price) end end end ! class SuperDownloader def download_file # Download from interwebs end end ! class S3Downloader < SuperDownloader def download_file # Now we're cool and user S3 to store our inventories end end !
29. Liskov Substitution Principle (LSP)
30. class FtpDownloader < GeneralDownloader def download_file # Here we do all the FTP connection to download our file end end ! class S3Downloader < GeneralDownloader def download_file # Now we're cool and user S3 to store our inventories end end ! class GeneralDownloader def download_file # get any url and download, more like wget end end
32. Interface Segregation Principle (ISP)
33. Want a good example?
34. Devise
35. class User < ActiveRecord::Base devise :database_authenticatable, :registerable, :recoverable, :rememberable, :trackable, :validatable end class Admin < ActiveRecord::Base devise :database_authenticatable, :registerable, :recoverable, :trackable, :validatable end
36. Dependency Inversion Principle (DIP)
37. public class RemoteControl { public RemoteControl(TV tv) { this.tv = tv; } ! public void pressPowerButton() { if (this.tv.isOn()) { this.tv.off(); System.out.println("turning off!"); } else { this.tv.on(); System.out.println("turning on!"); } } }
38. OH! You should use a interface
39. public class RemoteControl { public RemoteControl(TurnableOnOff obj) { this.obj = obj; } ! public void pressPowerButton() { if (this.obj.isOn()) { this.obj.off(); System.out.println("turning off!"); } else { this.obj.on(); System.out.println("turning on!"); } } } ! public interface TurnableOnOff { public void off(); public boolean isOn(); public void on(); } ! public class TV implements TurnableOnOff { // ... }
40. Back to Ruby
42. class RemoteControl def initialize(turnable_on_off) @obj = turnable_on_off end ! def press_power_button obj.on? ? obj.off : obj.on end end ! class TV def on? ; end def on ; end def off ; end end ! class Radio def on? ; end def on ; end def off ; end end
43. But why should I care?
44. time Good Design Bad Design
45. time Good Design Bad Design refactoring
46. time Good Design Bad Design refactoring cost
47. time Good Design Bad Design refactoring cost
48. time Good Design Bad Design Here is when you star to CRY! refactoring cost
49. We are hiring! Estamos contratando!
50. We are hiring! Estamos contratando!
51. Questions? ¿Consultas? Perguntas? @filipebarcos Filipe Costa
52. Thanks! ¡Gracias! Obrigado! @filipebarcos Filipe Costa