Building Maintainable Rails Apps

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Building Maintainable Rails Apps @andypike

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Thank you!

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Charlie

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Allow myself to introduce… …myself

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Andy Pike

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Rails Core Team Ruby Core Team RSpec Core Team

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Any Core Team

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Awesome Famous Inc.

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I’m a freelance developer You can hire me I can totally 100% help you You can hire me!

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You can follow me: (You can also hire me!) @andypike

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Basic Visual Basic C++ Classic ASP .NET Rails PHP

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$ rails new awesome_project

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“Programmers at work maintaining a Ruby on Rails application” classicprogrammerpaintings.com

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∞ Light speed Fast Medium Slow Age of project Time to develop a feature Heat death of the universe

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Why?

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Skinny Controller

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Fat Model

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Fat Controller

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Obese Model

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What would DHH do?

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How do we improve things?

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Single Responsibility Principle A class should have one, and only one, reason to change.

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Entry point HTTP Run appropriate logic Controllers

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Data Persistence Associations Closely related logic Models

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Generate markup from data Views

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Where does the other code go?

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Dealing with input Business Logic Database Queries UI Logic Rails is Missing Constructs For: ȴ 

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andypike / rectify

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Form Objects Command Objects Query Objects Presenter Objects Rectify Provides: ȴ 

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Contrived Examples Use of imagination required WARNING

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Dealing with input Business Logic UI Logic Database Queries ȴ 

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Context

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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

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class User < ActiveRecord::Base has_many :things validates :email, :presence => true end

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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

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class User < ActiveRecord::Base has_many :things validates :email, :presence => true validates :age, :presence => true, :if => :persisted? end

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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

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Context Whitelisted attributes and validations are in different places.

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Context Increases Complexity

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Structure

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= 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"

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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

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Structure Forms matching the database structure

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Types

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{ "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

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Types Param values are Strings

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Introducing: Form Objects

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Deals with input data Whitelists parameters Validations Indirection from models Type coercion

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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

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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

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= 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"

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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)

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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

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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

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Business Logic ȴ Dealing with input UI Logic Database Queries 

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Where does it go? ȴ

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In the controller? ȴ

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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

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Controller Not HTTP Not the controller’s concern ȴ

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In the model? ȴ

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def create @user = User.new(user_params) if @user.register redirect_to dashboard_path else render :new end end ȴ

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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

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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

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Model Leads to God Objects Harder to understand Too many responsibilities ȴ

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Service Objects ȴ

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class UserService def self.register(params) # stuff end # every other method moved # from the user model end ȴ

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(Misunderstood) Service Objects Ends up being a replacement for the model ȴ

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Introducing: Command Objects ȴ

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Encapsulate a business task Named using Verbs Called by the Controller Multiple results No callbacks ȴ

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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

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def create @form = RegisterUserForm.from_params(params) RegisterUser.call(@form) do on(:ok) { redirect_to dashboard_path } on(:invalid) { render :new } end end ȴ

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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

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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

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Business Logic Dealing with input UI Logic Database Queries ȴ 

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WAT? 

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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 

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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 

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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 

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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 

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Queries in the Model Can lead to large models Harder to understand 

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Introducing: Query Objects 

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Encapsulates a database query and logic required to build it 

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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 

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class UsersOlderThan < Rectify::Query def initialize(age) @age = age end def query User.where("age > ?", @age) end end UsersOlderThan.new(25).count 

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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 

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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 

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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 

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

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UI Logic Business Logic Dealing with input Database Queries ȴ 

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Views

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<% 8.upto(22) do |hour| %>

<%= "#{hour.to_s.rjust(2, '0')}:00" %>

<% end %>

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Helpers

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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 %>

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<% if current_user.admin? && current_user.company.plan.paid? %> <%= link_to "#{current_user.company.name} Billing", account_path %> <% end %>

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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

<%= billing_link %>

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Introducing: Presenter Objects

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Encapsulates view logic Full page or component

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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

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class CalendarController < ApplicationController include Rectify::ControllerHelpers def show present CalendarPresenter.new end end <% presenter.hours do |hour| %>

<%= hour %>

<% end %>

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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

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class AccountsController < ApplicationController include Rectify::ControllerHelpers def show present BillingPresenter.new(:user => current_user) end end

<%= presenter.billing_link %>

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def show present BillingPresenter.new(:user => current_user) present MenuPresenter.new, :for => :menu present FooterPresenter.new, :for => :footer end <%= presenter(:menu).login_link %>

<%= presenter.billing_link %>

<%= presenter(:footer).copyright_notice %>

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Testing

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RSpec Setup # spec/rails_helper.rb require "rectify/rspec" RSpec.configure do |config| config.include Rectify::RSpec::Helpers end

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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

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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")

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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

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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

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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

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Testing Presenters it "renders the billing link" do presenter = BillingPresenter.new(:user => admin_user) expect(presenter.billing_link).to eq('Billing') 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('Billing') end

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What’s the point of all this?

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Avoid controllers and models growing to an unmanageable size and complexity

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pragmatic /praɡˈmatɪk/ adjective dealing with things sensibly and realistically in a way that is based on practical rather than theoretical considerations.

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∞ Light speed Fast Medium Slow Age of project Time to develop a feature Interesting point

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Tweet me questions or catch up with me later Don’t forget, you can hire me! @andypike