Building Maintainable Rails Apps

This talk was given at RubyC in Kiev in June 2016.

The video for this talk is here: http://andypike.com/blog/conferences/rubyc-2016/

We love Rails! When the project is young we move at light speed! As time moves on, code entangles and development slows. In this talk we will explore why this happens and ways you can avoid it. You will learn a different “Rails Way” that retains what we love and adds good object orientated design which makes your app easier to maintain. We will see how to implement form objects, service objects and presenters in a Rails app to separate responsibilities and aid maintainability. If your Rails app is hard to maintain or you would like to learn techniques to avoid it, this talk is for you.

Transcript

1. Building Maintainable Rails Apps @andypike
3. Thank you!
4. Charlie
5. Allow myself to introduce… …myself
6. Andy Pike
7. Rails Core Team Ruby Core Team RSpec Core Team
8. Any Core Team
10. Awesome Famous Inc.
11. I’m a freelance developer You can hire me I can totally 100% help you You can hire me!
12. You can follow me: (You can also hire me!) @andypike
15. Basic Visual Basic C++ Classic ASP .NET Rails PHP
16. $ rails new awesome_project
22. “Programmers at work maintaining a Ruby on Rails application” classicprogrammerpaintings.com
23. ∞ Light speed Fast Medium Slow Age of project Time to develop a feature Heat death of the universe
24. Why?
26. Skinny Controller
27. Fat Model
28. Fat Controller
29. Obese Model
30. What would DHH do?
33. How do we improve things?
34. Single Responsibility Principle A class should have one, and only one, reason to change.
35. Entry point HTTP Run appropriate logic Controllers
36. Data Persistence Associations Closely related logic Models
37. Generate markup from data Views
38. Where does the other code go?
39. Dealing with input Business Logic Database Queries UI Logic Rails is Missing Constructs For: ȴ 
40. andypike / rectify
41. Form Objects Command Objects Query Objects Presenter Objects Rectify Provides: ȴ 
42. Contrived Examples Use of imagination required WARNING
43. Dealing with input Business Logic UI Logic Database Queries ȴ 
44. Context
45. class UsersController < ApplicationController def new @user = User.new end def create @user = User.new(user_params) if @user.save redirect_to dashboard_path else render :new end end private def user_params params.require(:user).permit(:first_name, :last_name, :email) end end
46. class User < ActiveRecord::Base has_many :things validates :email, :presence => true end
47. def update @user = User.find(params[:id]) if @user.update(update_user_params) redirect_to dashboard_path else render :edit end end private def create_user_params params.require(:user).permit(:first_name, :last_name, :email) end def update_user_params params.require(:user).permit(:first_name, :last_name, :email, :age) end
48. class User < ActiveRecord::Base has_many :things validates :email, :presence => true validates :age, :presence => true, :if => :persisted? end
49. def update @user = User.find(params[:id]) user_params = current_user.admin? ? admin_user_params : update_user_params if @user.update(user_params) redirect_to dashboard_path else render :edit end end private # def create_user_params # def update_user_params def admin_user_params params.require(:user).permit(:first_name, :last_name, :email, :age, :role) end
50. Context Whitelisted attributes and validations are in different places.
51. Context Increases Complexity
52. Structure
53. = simple_form_for @company do |f| = f.input :name = f.simple_fields_for :users_attributes, @user do |u| = u.input :full_name = u.input :email = f.submit "Sign Up"
54. class Company < ActiveRecord::Base has_many :users accepts_nested_attributes_for :users end class User < ActiveRecord::Base belongs_to :company def full_name [first_name, last_name].join(" ") end def full_name=(name) names = name.split(" ", 2) self.first_name = names.first self.last_name = names.last end end
55. Structure Forms matching the database structure
56. Types
57. { "utf8" => "✓", "authenticity_token" => "gjsQSQXchsBI7yuz…", "user" => { "full_name" => "Andy Pike", "age" => "25" }, "commit" => "Save", "id" => "1" } 2016 - params[:user][:age] # => TypeError: String can't be coerced into Fixnum
58. Types Param values are Strings
59. Introducing: Form Objects
60. Deals with input data Whitelists parameters Validations Indirection from models Type coercion
61. class RegisterUserForm < Rectify::Form attribute :first_name, String attribute :last_name, String attribute :email, String validates :email, :presence => true end class UpdateProfileForm < Rectify::Form attribute :first_name, String attribute :last_name, String attribute :email, String attribute :age, Integer validates :email, :presence => true validates :age, :presence => true end
62. class RegisterForm < Rectify::Form attribute :company_name, String attribute :full_name, String attribute :email, String validates :email, :presence => true def first_name name_parts.first end def last_name name_parts.last end private def name_parts full_name.split(" ", 2) end end
63. = simple_form_for @company do |f| = f.input :name = f.simple_fields_for :users_attributes, @user do |u| = u.input :full_name = u.input :email = f.submit "Sign Up" # vs = simple_form_for @form do |f| = f.input :company_name = f.input :full_name = f.input :email = f.submit "Sign Up"
64. def new @form = RegisterUserForm.new end def create @form = RegisterUserForm.from_params(params) if @form.valid? # Do something interesting else render :new end end # no strong_parameters :o)
65. def edit user = User.find(params[:id]) @form = UpdateProfileForm.from_model(user) end def update @form = UpdateProfileForm.from_params(params) # @form.first_name => "Andy Pike" # @form.age => 25 # @form.attributes => { :first_name => "Andy Pike" ... } if @form.valid? # Do something interesting else render :edit end end
66. class AccountHolderForm < UserForm attribute :age, Integer attribute :colours, Array attribute :address, AddressForm attribute :contacts, Array[ContactForm] end @form = AccountHolderForm.from_params(params) @form.valid? # validates the form, superclass, # nested forms and array of forms
68. Business Logic ȴ Dealing with input UI Logic Database Queries 
69. Where does it go? ȴ
70. In the controller? ȴ
71. UserMailer.confirmation(@user).deliver_later case @user.potential_revenue when :low logger.info("We don’t care about #{@user.full_name}") when :medium CRM.add(@user) when :high CRM.add(@user) SMS.notify_sales_high_value_customer(@user) end redirect_to dashboard_path else render :new end end ȴ def create @user = User.new(user_params) if @user.save
72. Controller Not HTTP Not the controller’s concern ȴ
73. In the model? ȴ
74. def create @user = User.new(user_params) if @user.register redirect_to dashboard_path else render :new end end ȴ
75. class User def register if save UserMailer.confirmation(self).deliver_later case potential_revenue when :low logger.info("We don’t care about #{full_name}") when :medium CRM.add(self) when :high CRM.add(self) SMS.notify_sales_high_value_customer(self) end end persisted? end end ȴ
76. class User def register return false unless save send_confirmation send("#{potential_revenue}_potential_revenue") true end def send_confirmation UserMailer.confirmation(self).deliver_later end def low_potential_revenue def medium_potential_revenue def high_potential_revenue end ȴ
77. ȴ
78. Model Leads to God Objects Harder to understand Too many responsibilities ȴ
79. Service Objects ȴ
80. class UserService def self.register(params) # stuff end # every other method moved # from the user model end ȴ
81. ȴ
82. (Misunderstood) Service Objects Ends up being a replacement for the model ȴ
83. Introducing: Command Objects ȴ
84. Encapsulate a business task Named using Verbs Called by the Controller Multiple results No callbacks ȴ
85. class RegisterUser < Rectify::Command def initialize(form) @form = form end def call return broadcast(:invalid) if @form.invalid? # Your code goes here broadcast(:ok) end private # def do_something # end end ȴ
86. def create @form = RegisterUserForm.from_params(params) RegisterUser.call(@form) do on(:ok) { redirect_to dashboard_path } on(:invalid) { render :new } end end ȴ
87. class PlaceOrder < Rectify::Command def initialize(form, customer) @form = form @customer = customer end def call return broadcast(:invalid) if @form.invalid? return broadcast(:card_expired) if card_expired? transaction do order = create_order update_crm notify_customer broadcast(:ok, order) end end private def create_order ȴ
88. def create @form = OrderForm.from_params(params) PlaceOrder.call(@form, current_user) do on(:ok) { |order| redirect_to order_path(order) } on(:invalid) { render :new } on(:card_expired) { redirect_to billing_path } end end ȴ
89. ȴ
90. Business Logic Dealing with input UI Logic Database Queries ȴ 
91. WAT? 
92. class UsersController < ApplicationController def index @users = User.where(:plays_minecraft => true) end def show @user = User.find(params[:id]) @recent_orders = @user.orders.where("created_at > ?", 5.days.ago) end end 
93. class User < ActiveRecord::Base has_many :orders scope :cool, -> { where(:plays_minecraft => true) } def recent_orders orders.where("created_at > ?", 5.days.ago) end end 
94. def self.programmer_admins important_value = some_logic_required_by_the_query active .admin .programmer .where("SOME SQL ?", important_value) .where("SOME MORE REALLY LONG COMPLEX SQL") .where("SOME MORE REALLY REALLY LONG COMPLEX SQL") .order(:created_at => :desc) end def self.some_logic_required_by_the_query # Involved calculations end 
95. def self.important_orders sql = <<-SQL.strip_heredoc WITH regional_sales AS ( SELECT region, SUM(amount) AS total_sales FROM orders GROUP BY region ), top_regions AS ( SELECT region FROM regional_sales WHERE total_sales > (SELECT SUM(total_sales)/10 FROM regional_sales) ) SELECT region, product, SUM(quantity) AS product_units, SUM(amount) AS product_sales FROM orders WHERE region IN (SELECT region FROM top_regions) AND amount > :amount GROUP BY region, product; SQL Order.find_by_sql([sql, { :amount => 50 }]) end 
96. Queries in the Model Can lead to large models Harder to understand 
97. Introducing: Query Objects 
98. Encapsulates a database query and logic required to build it 
99. class CoolUsers < Rectify::Query def query User.where(:plays_minecraft => true) end end # Usage: CoolUsers.new.count CoolUsers.new.first CoolUsers.new.exists? CoolUsers.new.none? CoolUsers.new.to_a CoolUsers.new.map(&:age) # All Enumerable methods CoolUsers.new.each do |user| puts user.name end 
100. class UsersOlderThan < Rectify::Query def initialize(age) @age = age end def query User.where("age > ?", @age) end end UsersOlderThan.new(25).count 
101. class UsersWithBlacklistedEmail < Rectify::Query def initialize(blacklist) @blacklist = blacklist end def query User.where(:email => blacklisted_emails) end private def blacklisted_emails @blacklist.map { |b| b.email.strip.downcase } end end 
102. active_users_over_20 = ActiveUsers.new | UsersOlderThan.new(20) active_users_over_20 = ActiveUsers.new.merge(UsersOlderThan.new(20)) active_users_over_20 = Rectify::Query.merge( ActiveUsers.new, UsersOlderThan.new(20) ) active_users_over_20.count 
103. class UsersOverUsingSql < Rectify::Query include Rectify::SqlQuery def initialize(age) @age = age end def model User end def sql <<-SQL.strip_heredoc SELECT * FROM users WHERE age > :age ORDER BY age ASC SQL end def params { :age => @age } end end 
104. 
105. UI Logic Business Logic Dealing with input Database Queries ȴ 
106. Views
107. <% 8.upto(22) do |hour| %> <div class="timestamp"><%= "#{hour.to_s.rjust(2, '0')}:00" %></div> <% end %>
108. Helpers
109. module ApplicationHelper def hours 8.upto(22) do |hour| time = "#{hour.to_s.rjust(2, '0')}:00" content_tag(:div, time, :class => "timestamp") end end end <%= hours %>
110. <% if current_user.admin? && current_user.company.plan.paid? %> <%= link_to "#{current_user.company.name} Billing", account_path %> <% end %>
111. module ApplicationHelper def billing_link return unless current_user.admin? && current_user.company.plan.paid? link_to "#{current_user.company.name} Billing", account_path end end <div> <%= billing_link %> </div>
112. Introducing: Presenter Objects
113. Encapsulates view logic Full page or component
114. class CalendarPresenter < Rectify::Presenter def hours 8.upto(22) do |hour| yield formatted_time(hour) end end private def formatted_time(hour) "#{hour.to_s.rjust(2, '0')}:00" end end
115. class CalendarController < ApplicationController include Rectify::ControllerHelpers def show present CalendarPresenter.new end end <% presenter.hours do |hour| %> <div class="timestamp"><%= hour %></div> <% end %>
116. class BillingPresenter < Rectify::Presenter attribute :user, User def billing_link return unless show_billing? link_to "#{user.company.name} Billing", account_path end private def show_billing? user.admin? && user.company.plan.paid? end end
117. class AccountsController < ApplicationController include Rectify::ControllerHelpers def show present BillingPresenter.new(:user => current_user) end end <div> <%= presenter.billing_link %> </div>
118. def show present BillingPresenter.new(:user => current_user) present MenuPresenter.new, :for => :menu present FooterPresenter.new, :for => :footer end <nav><%= presenter(:menu).login_link %></nav> <div><%= presenter.billing_link %></div> <footer> <%= presenter(:footer).copyright_notice %> </footer>
120. Testing
121. RSpec Setup # spec/rails_helper.rb require "rectify/rspec" RSpec.configure do |config| config.include Rectify::RSpec::Helpers end
122. Testing Forms RSpec.describe UserForm do subject { described_class.new(:name => "Andy") } it "is valid with valid attributes" do expect(subject).to be_valid end describe "#name" do it "cannot be blank" do subject.name = "" expect(subject).to be_invalid end end end
123. Stubbing Forms form = stub_form(:valid? => true, :name => "Andy") form.valid? # => true form.invalid? # => false form.name # => "Andy" form.attributes # => { :name => "Andy" } # or form = Rectify::StubForm.new(:valid? => true, :name => “Andy")
124. Testing Commands ȴ RSpec.describe PlaceOrder do context "when the form is valid" do it "broadcasts :ok" do form = stub_form(:valid? => true) command = described_class.new(form) expect { command.call }.to broadcast(:ok) end end end
125. Testing Queries  RSpec.describe UsersOlderThan do it "returns users older than the supplied age" do older = create(:user, :age => 10) younger = create(:user, :age => 8) expect(UsersOlderThan.new(9).to_a).to match_array([older]) end end
126. Stubbing Queries  it "returns the only user's age" do stub_query(AllUsers, :results => User.new(:age => 25)) expect(subject.total_ages).to eq(25) end it "returns the sum of all users ages" do stub_query(AllUsers, :results => [ User.new(:age => 25), User.new(:age => 20) ]) expect(subject.total_ages).to eq(45) end
127. Testing Presenters it "renders the billing link" do presenter = BillingPresenter.new(:user => admin_user) expect(presenter.billing_link).to eq('<a href="/billing">Billing</a>') end it "renders the billing link for current_user” do presenter = BillingPresenter.new presenter.attach_controller(ApplicationController) # use current_user expect(presenter.billing_link).to eq('<a href="/billing">Billing</a>') end
128. What’s the point of all this?
129. Avoid controllers and models growing to an unmanageable size and complexity
131. pragmatic /praɡˈmatɪk/ adjective dealing with things sensibly and realistically in a way that is based on practical rather than theoretical considerations.
132. ∞ Light speed Fast Medium Slow Age of project Time to develop a feature Interesting point
135. Tweet me questions or catch up with me later Don’t forget, you can hire me! @andypike