Architecting a Rails application

How using design patterns beyond MVC will help you write better architected Rails applications.

Transcript

1. Architecting a Rails app A S H O R T S T O R Y by Luke Randall
2. PHP The horrors of (my)
3. Rails thinks for me + has a place for everything
4. Yay problem solved!
5. Hmm... problem solved?
6. complex? What makes your app
7. Business logic
8. Business logic everywhere!
9. Views
10. <% Post.last(3).each do |post| %> ... <% end %> Exhibit 1a
11. <% if current_user and current_user.admin? %> This counts as logic <% end %> Exhibit 1B
12. Presenters You should be using
13. presenter’s Your structure should reflect the views structure
14. Controllers
15. Picture a controller with lots of logic Exhibit 2a
16. Fat models Skinny controllers
17. def index @posts = Post.published .with_tag(params[:tag]) .reorder('published_at DESC') .include(:comments) .limit(5) end Exhibit 2B
18. Controllers should be a thin mapping between a user request and your actual API
19. Models
20. class User < ActiveRecord::Base extend ActiveSupport::Memoizable has_and_belongs_to_many :questionable_titles has_and_belongs_to_many :group_collectives belongs_to :preferred_group_collective, :class_name => 'GroupCollective' acts_as_authentic acts_as_audited :except => [:perishable_token, :last_request_at, :login_count, :last_login_at] i_want_to_hear_from_your_via :email validates_presence_of :name validate :has_an_authorized_fascist_score validates_format_of :password, :with => /(([0-9]+[A-Za-z]+)|([A-Za-z]+[0-9]+)).*/, :if => :require_password?, :message => "must include at least one number and one letter" def first_name name.andand.split.andand.first end def default_group_collective @default_group_collective ||= preferred_group_collective || group_collectives.first end def recent_group_collectives return [] unless recent_group_collectives_ids GroupCollective.find(:all, :conditions => ["id IN (?)", recent_group_collectives_ids.split(',')]) end def add_to_recent_group_collectives(group_collective_id) recent = recent_group_collectives_ids recent ||= '' ids = recent.split(',').insert(0, group_collective_id.to_s).uniq.select {|a| a}.first(10).join(',') update_attribute(:recent_group_collectives_ids, ids) end def remove_from_recent_group_collectives(group_collective_id) list = recent_group_collectives_ids.split(',') list.delete("#{group_collective_id}") self.recent_group_collectives_ids = list.join(',') self.save end def deliver_password_reset_instructions! reset_perishable_token! Notifier.deliver_password_reset_instructions(self) end # There are tnhaoeuhsaou oesnhuasonthu soaetnhu anoth: # * ntaohue sntahou snoatuhsntah stnoehu # * anstoeuh satnou sntahsntuha osnteh usnth # * sanoteh usnahsntuh santhousnthaosnthao sntuh # For more info snahtousa usahtnoeu snathousaotnhsn def is_group_superintendant?(space_station) is_space_station_superintendant?(space_station) && space_station.group_space_station? end def is_consolidation_superintendant?(space_station) is_space_station_superintendant?(space_station) && space_station.consolidation_space_station? end def is_space_station_superintendant?(space_station) return true if has_questionable_title?('super_user') # The user is a member of one of the space_station's group_collectives group_collectives.exists?(:space_station_id => space_station.id) && # and the user has the 'space_station_superintendant' questionable_title has_questionable_title?('space_station_superintendant') end def is_superintendant? has_questionable_title?('superintendant') || has_questionable_title?('super_user') end #memoize :is_superintendant? def is_master_and_commander_for_the_free_world? has_questionable_title?('super_user') end #memoize :is_master_and_commander_for_the_free_world? def authorized_to_access_group_collective?(group_collective_id, space_station = nil) log_time("authorizing #{email} for group_collective #{group_collective_id}", lambda { return false unless GroupCollective.exists?(group_collective_id) # If he is a master_and_commander_for_the_free_world he can access any group_collective return true if is_master_and_commander_for_the_free_world? # if the group_collective is associated with him then he can access it return true if group_collectives.exists?(group_collective_id) # The space_station parameter is required for authorization beyond this point return false if space_station.nil? # if he is a space_station_superintendant on a 'Group' space_station then he can only access the group_collective if it # belongs to the current space_station if is_group_superintendant?(space_station) return true if GroupCollective.exists?(:id => group_collective_id, :space_station_id => space_station.id) # if he is a consolidation_superintendant he can only access the group_collective if it # is beneath him in the consolidation tree elsif is_consolidation_superintendant?(space_station) return false unless space_station.group_collectives.exists?(:id => group_collective_id) # return false if the group_collective is not on his space_station # He is authorized if the group_collective is a decendent of any of his associated group_collectives group_collective_in_question = space_station.group_collectives.find(group_collective_id) return group_collectives.any? {|group_collective| group_collective_in_question.descendent_of?(group_collective)} end # he has not been authorized at any level return false }) end def has_many_group_collectives? group_collectives.size > 1 end def primary_group_collective return nil if group_collectives.empty? return group_collectives.first(:conditions => {:master_group_collective => true}) if group_collectives.exists?(:master_group_collective => true) group_collectives.first end def has_no_group_collective? group_collectives.empty? end def add_group_collective(group_collective) self.group_collectives << group_collective self.save! end # questionable_title based access methods # has_questionable_title? is used by questionable_title_requirement def has_questionable_title?(questionable_title_in_question) @_questionable_titles_list = self.questionable_titles.collect(&:name) @_questionable_titles_list.include?(questionable_title_in_question.to_s) end def authorised_for_questionable_title?(questionable_title_in_question) # Check if the use qualifies for the questionable_title_in_question implicitly # due to a higher questionable_title that they posses if questionable_titleS_AND_SUPERIORS[questionable_title_in_question].any?{|r| has_questionable_title?(r)} return true # The user does not qualify implicitly (they own no higher questionable_title). Check for # the questionable_title_in_question explicitly. elsif has_questionable_title?(questionable_title_in_question) return true end return false end def update_questionable_titles(questionable_titles) return valid? if questionable_titles.blank? questionable_titles.each do |questionable_title_name, status| delete_questionable_title(questionable_title_name) if status.to_i == 0 add_questionable_title(questionable_title_name) if status.to_i == 1 end return valid? end def delete_questionable_title(questionable_title_name) return unless self.has_questionable_title?(questionable_title_name) self.questionable_titles.delete(self.questionable_titles.find(:first, :conditions => {:name => questionable_title_name})) end def add_questionable_title(questionable_title_name) return false if questionable_title_name == 'super_user' return true if self.has_questionable_title?(questionable_title_name) self.questionable_titles << questionable_title.find_by_name(questionable_title_name) self.save end def authorised_fascist_scores return FASCIST_SCORES_WITH_COMMUNISM if is_superintendant? || is_master_and_commander_for_the_free_world? fascist_scores = questionable_titles.collect {|questionable_title| questionable_title.view_fascist_score} ordered_fascist_scores = [] # let's try loop through this so that the allowed fascist_scores are in the propers order, yo FASCIST_SCORES_WITH_COMMUNISM.each do |view_fascist_score| ordered_fascist_scores << view_fascist_score if fascist_scores.include?(view_fascist_score) end return ordered_fascist_scores end def has_an_authorized_fascist_score return if authorised_for_questionable_title?('superintendant') errors.add_to_base 'User must have at least one fascist_score that they are authorized to access.' if authorised_fascist_scores.blank? end end Exhibit 3a
21. The only letter left in MVC
22. Models are a catch-all for business logic
23. Models are a catch-all for business logic complexity
24. All models eventually have one billion methods doing completely di erent things * * actual number may vary
25. Single responsibility Open closed Liskov substitution Interface segregation Dependency inversion
26. “The problem with object-oriented languages is they’ve got all this implicit environment that they carry around with them. You wanted a banana but what you got was a gorilla holding the banana and the entire jungle.” Joe Armstrong
27. means you’re doing something Pain in tests wrong
28. class oriented vs object oriented
29. Meaning comes from casting data into a role
30. Meaning comes from casting data into a role what the system is what the system does
31. user.extend FriendApprover user.approve(friend_request) * * stolen shamelessly from Jim Gay’s blog
32. user.extend FriendApprover user.approve(friend_request) * * stolen shamelessly from Jim Gay’s blog data role
33. Single responsibility Open closed Liskov substitution Interface segregation Dependency inversion
34. Roles are reusable Clearly defined interface
35. Roles are testable Use plain old Ruby objects
36. context roles have a
37. class AddToCartContext attr_reader :user, :book def self.call(user_id, book_id) AddToCartContext.new(user_id, book_id).call end def initialize(user_id, book_id) @user = User.find(user_id) @book = Book.find(book_id) @user.extend Customer end def call @user.add_to_cart(@book) end end * * stolen shamelessly from Mike Pack’s blog context readable logic
38. Controllers should be a thin mapping between a user request and your actual API Replay
39. Contexts are your actual API
40. Contexts read like the logic they implement
41. Business logic expressed in a first class, easily understood, easily modified, easily tested, entity
42. Guide us O Great Wizard!
43. DCI data context interaction
44. I invented MVC and DCI for each other “ ” (not actually) Trygve Reenskaug
45. extra overhead? what about the
46. “Architectural decisions are tradeoffs” Me, right now + many others
47. “A good architecture allows major decisions to be deferred ” Robert “Uncle Bob” Martin
48. We’re deferring adding bloaty, messy logic to the moment it is needed
49. Use this
50. Luke Randall @luke_randall lukerandall.github.com