Generate a new Rails app w/ Postgres support

rails new myapp --database=postgresql

Without minitest

rails new myapp -T

Rails Model

describe 'associations' do
  it { should belong_to(:parent).optional }
  it { should belong_to(:category).class_name('MenuCategory') }
  it { should have_many(:childs) }

describe 'indexes' do
  it { should have_db_index(:parent_id) }

describe 'validations' do
  it { should validate_presence_of(:name) }
  it { should validate_uniqueness_of(:name).scoped_to(:category_id) }
  it { should allow_value('https://foo.com').for(:website_url) }

  # class UserProfile
  #   include ActiveModel::Model
  #   attr_accessor :birthday_as_string
  #   validates_format_of :birthday_as_string,
  #     with: /^(\d+)-(\d+)-(\d+)$/,
  #     on: :create
  # end

  it { should     allow_value('2013-01-01').for(:birthday_as_string).on(:create) }
  it { should_not allow_value('2013/01/01').for(:birthday_as_string).on(:create) }

describe 'delegations' do
  it { should delegate_method(:name).to(:brand).with_prefix.allow_nil }
  it { should delegate_method(:name).to(:category).with_prefix.allow_nil }

Rails Enum

enum role: {
 user: 0,
 admin: 1,
 other: 99

Rails Validations

validates :name, presence: true
validates :terms_of_service, acceptance: true
validates :terms_of_service, acceptance: { message: 'must be abided' }
validates :size, inclusion: { in: %w(small medium large),
  message: "%{value} is not a valid size" }
validates :name, length: { minimum: 2 }
validates :bio, length: { maximum: 500 }
validates :password, length: { in: 6..20 }
validates :registration_number, length: { is: 6 }
validates :points, numericality: true
validates :games_played, numericality: { only_integer: true }
validates :email, uniqueness: true

Custom Validations

Testing custom validation with error message.

   class UserProfile
     include ActiveModel::Model
     attr_accessor :sports_team

     validate :sports_team_must_be_valid


     def sports_team_must_be_valid
       if sports_team !~ /^(Broncos|Titans)$/i
         self.errors.add :chosen_sports_team,
           'Must be either a Broncos fan or a Titans fan'

   RSpec.describe UserProfile, type: :model do
     it do
       should allow_value('Broncos', 'Titans').
         with_message('Must be either a Broncos or Titans fan',
           against: :chosen_sports_team


Create a route that maps a URL to the controller action

# config/routes.rb
get 'welcome' => 'pages#home'

Shorthand for connecting a route to a controller/action

# config/routes.rb
get 'photos/show'

# The above is the same as:
get 'photos/show', :to 'photos#show'
get 'photos/show' => 'photos#show'

Automagically create all the routes for a RESTful resource

# config/routes.rb
resources :photos
HTTP Verb Path Controller#Action Used for
GET /photos photos#index display a list of all photos
GET /photos_new photos#new return an HTML form for creating a new photo
POST /photos photos#create create a new photo
GET /photos/:id photos#show display a specific photo
GET /photos/:id/edit photos#edit return an HTML form for editing a photo
PATCH/PUT /photos/:id photos#update update a specific photo
DELETE /photos/:id photos#destroy delete a specific photo

Create resources for only certain actions

# config/routes.rb
resources :photos, :only => [:index]

# On the flip side, you can create a resource with exceptions
resources :photos, :except => [:new, :create, :edit, :update, :show, :destroy]

Create a route to a static view, without an action in the controller

# config/routes.rb
# If there's a file called 'about.html.erb' in 'app/views/photos', this file will be
#   automatically rendered when you call localhost:3000/photos/about
get 'photos/about', to: 'photos#about'

Reference: http://guides.rubyonrails.org/routing.html


Generate a new controller

Note: Name controllers in Pascal case and pluralize

$ rails g controller Photos

Generate a new controller with default actions, routes and views

$ rails g controller Photos index show

Reference: http://guides.rubyonrails.org/action_controller_overview.html


Generate a model and create a migration for the table

Note: Name models in Pascal case and singular

$ rails g model Photo

Generate a model and create a migration with table columns

$ rails g model Photo path:string caption:text

The migration automatically created for the above command:

class CreatePhotos < ActiveRecord::Migration
  def change
    create_table :photos do |t|
      t.string :path
      t.text :caption

      t.timestamps null: false

Reference: http://guides.rubyonrails.org/active_model_basics.html


Migration Data Types

  • :boolean
  • :date
  • :datetime
  • :decimal
  • :float
  • :integer
  • :primary_key
  • :references
  • :string
  • :text
  • :time
  • :timestamp

When the name of the migration follows the format AddXXXToYYY followed by a list of columns, it will add those columns to the existing table

$ rails g migration AddDateTakenToPhotos date_taken:datetime

The above creates the following migration:

class AddDateTakenToPhotos < ActiveRecord::Migration[5.0]
  def change
    add_column :photos, :date_taken, :datetime

You can also add a new column to a table with an index

$ rails g migration AddDateTakenToPhotos date_taken:datetime:index

The above command generates the following migration:

class AddDateTakenToPhotos < ActiveRecord::Migration[5.0]
  def change
    add_column :photos, :date_taken, :datetime
    add_index :photos, :date_taken

The opposite goes for migration names following the format: RemoveXXXFromYYY

$ rails g migration RemoveDateTakenFromPhotos date_taken:datetime

The above generates the following migration:

class RemoveDateTakenFromPhotos < ActiveRecord::Migration[5.0]
  def change
    remove_column :photos, :date_taken, :datetime


Scaffolding is great for prototypes but don’t rely too heavily on it: http://stackoverflow.com/a/25140503

$ rails g scaffold Photo path:string caption:text
$ rake db:migrate


View all the routes in an application

$ rake routes

Seed the database with sample data from db/seeds.rb

$ rake db:seed

Run any pending migrations

$ rake db:migrate

Rollback the last migration performed

NOTE: Be VERY careful with this command in production, it’s destructive and you could potentially lose data. Make sure you absolutely understand what will happen when you run it

$ rake db:rollback

Path Helpers

Creating a path helper for a route

# Creating a path helper for a route
get '/photos/:id', to: 'photos#show', as: 'photo'
# app/controllers/photos_controller.rb
@photo = Photo.find(17)
# View for the action
<%= link_to 'Photo Record', photo_path(@photo) %>

Path helpers are automatically created when specifying a resource in config/routes.rb

# config/routes.rb
resources :photos
HTTP Verb Path Controller#Action Named Helper
GET /photos photos#index photos_path
GET /photos/new photos#new new_photo_path
POST /photos photos#create photos_path
GET /photos/:id photos#show photo_path(:id)
GET /photos/:id/edit photos#edit edit_photo_path(:id)
PATCH/PUT /photos/:id photos#update photo_path(:id)
DELETE /photos/:id photos#destroy photo_path(:id)

Asset Pipeline

Access images in the app/assets/images directory like this:

<%= image_tag "rails.png" %>

Within views, link to JavaScript and CSS assets

<%= stylesheet_link_tag "application" %>
<%= javascript_include_tag "application" %>
<!-- Filenames are fingerprinted for cache busting -->
<link href="/assets/application-4dd5b109ee3439da54f5bdfd78a80473.css" media="screen"
rel="stylesheet" />
<script src="/assets/application-908e25f4bf641868d8683022a5b62f54.js"></script>

Reference: http://guides.rubyonrails.org/asset_pipeline.html

Form Helpers

Bind a form to a model for creating/updating a resource

Use this method if you’re using strong params to protect against mass assignment

# app/controllers/photos_controller.rb
def new
  @photo = Photo.new
# ERB view
<%= form_for @photo, url: {action: "create"}, html: {class: "nifty_form"} do |f| %>
  <%= f.text_field :path %>
  <%= f.text_area :caption, size: "60x12" %>
  <%= f.submit "Create" %>
<% end %>
<!-- HTML output -->
<form accept-charset="UTF-8" action="/photos/create" method="post" class="nifty_form">
  <input id="photos_path" name="photo[path]" type="text" />
  <textarea id="photos_caption" name="photo[caption]" cols="60" rows="12"></textarea>
  <input name="commit" type="submit" value="Create" />

Create a form with a custom action and method

<%= form_tag("/search", method: "get") do %>
  <%= label_tag(:q, "Search for:") %>
  <%= text_field_tag(:q) %>
  <%= submit_tag("Search") %>
<% end %>
<form accept-charset="UTF-8" action="/search" method="get">
  <input name="utf8" type="hidden" value="&#x2713;" />
  <label for="q">Search for:</label>
  <input id="q" name="q" type="text" />
  <input name="commit" type="submit" value="Search" />

Reference: http://guides.rubyonrails.org/form_helpers.html

Upload file ActiveStorage (via console or rake tasks)

pathname = Pathname.new(path_to_image)

    io: File.open(pathname),
    filename: pathname.basename.to_s,
    content_type: Rack::Mime.mime_type(pathname.extname)

Generate dummy SKU



Encode JWT / generate access token

def access_token
  secret = Rails.application.credentials.jwt[:secret_key]
  method = Rails.application.credentials.jwt[:algorithm]
  payload = {
    data: {email: email, full_name: full_name},
    iat: Time.now.to_i,
    sub: Rails.application.credentials.jwt[:subject]

  JWT.encode(payload, secret, method)

Decode JWT

JWT.decode(token, secret, true, { algorithm: method })[0]

Shoulda Matchers

RSpec.describe UserProfile, type: :model do
  it { should validate_presence_of(:name) }


describe UserProfile, type: :model do
  it { should validate_presence_of(:name) }