Ruby on Rails Cheatsheet

RAILS_CHEATSHEET.md

Ruby on Rails Cheatsheet

Architecture

Create a new application

Install the Rails gem if you haven't done so before

$ gem install rails

Generate a new Rails app w/ Postgres support

$ rails new my_app --database=postgresql

Start the Rails server

$ rails s

Routes

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

Controllers

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

Models

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
    end
  end
end

Migration for a foreign key:

rails g migration AddUserToPosts user:references

then, update the Post models:

class Post < ApplicationRecord
  belongs_to :user
end

and update the User model:

class User < ApplicationRecord
  has_many :posts, foreign_key: :user_id, dependent: :destroy
  # Validations
  validates_presence_of :name, :email
end

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

Migrations

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
  end
end

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
  end
end

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
  end
end

Scaffolding

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

Rake

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

How can you know about rake commands:

rake -T

You can even limit by namespace, such as db:

rake -T db

Initialize the database

$ rake db:create

Cache enable/disable

$ rake dev:cache

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

Rollback the last migration performed

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
end

# 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" />
</form>

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" />
</form>

Deploy a rails app

Prepartion for heroku deploy:

• Remove sqlite3 gem from top of application to within group :development, :test do block
• Create a group production -> If using Rails 5

group :production do
  gem 'pg', '~> 0.11'
end

• Save Gemfile

• Run bundle install --without production to update Gemfile.lock file

• Commit your changes to git repo ->

git add -A
git commit -m "Make app production ready"

Command to install heroku toolbelt to your local environment, cloud9 already has the heroku toolbelt installed, you can check it by typing in heroku --version:

wget -qO- https://toolbelt.heroku.com/install-ubuntu.sh | sh

Check heroku:

heroku -v

heroku version heroku # for list of common heroku commands From your app directory:

To login to your heroku account from your env ->

heroku login

To add your SSH key to your heroku account so you don't have to use username and password everytime ->

heroku keys:add

To create a new production version of your app hosted in heroku ->

heroku create

To push your application code to heroku (deploy your app) ->

git push heroku master

Ensure you have committed all your local changes to your git repo prior to pushing to heroku by checking git status

To change the name of your application ->

heroku rename newnameofyourapp

replace newnameofyourapp above with the name you'd like to give your app

Your app will then be accessible from the following browser URL ->

newnameofyourapp.herokuapp.com

If your app has a DB, run ->

heroku run rake db:migrate

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