Ruby On Rails (RoR) Cheatsheet

ruby_on_rails_cheatsheet.md

Ruby on Rails cheatsheet

Ruby on Rails Keywords

alias	defined?	FILE	not	then
and	do	for	or	true
BEGIN	else	if	redo	undef
begin	elsif	in	rescue	unless
break	END	LINE	retry	until
case	end	module	return	when
class	ensure	next	self	while
def	false	nil	super	yield

Basic Rails Architecture

Rails Commands

rails new name

Creates a new Ruby on Rails application with the given name.

rails new my_app --database=postgresql

Generate a new Rails app w/ Postgres support

rails generate scaffold name attribute:type

The scaffold command generates all the common things needed for a new resource. This includes controllers, models and views.

rails generate controller name

Creates a new controller and its respective views with the given name here.

rails generate model name attribute:type

Creates a new model with the given name here and its respective migration with attributes mentioned.

rails server

Launches a small web server named WEBrick which comes bundled with Ruby on port 3000

rails console

The console command lets you interact with your Rails application from the command line.

Rake Commands

rake db:create

Creates the database for the current environment

rake db:create:all

Creates the databases for all environments

rake db:drop

Drops the database for the current environment

rake db:drop:all

Drops the databases for all environments

rake db:migrate

Runs migrations for the current environment that have not run yet

rake db:rollback

Rolls back the last migration

rake db:seed

(only) runs the db/seed.rb file

rake db:migrate:redo

Runs (db:migrate:down db:migrate:up) or (db:rollback db:migrate) depending on the specified migration

rake db:migrate:reset

Runs db:drop db:create db:migrate

rake tmp:clear

Clears session, cache, and socket files

rake assets:precompile

Compile all the assets named in config.assets.precompile

Bundle Commands

bundle install

Install the current environment's gems to the system

bundle exec

Run the command in context of the bundle

bundle clean

Cleans up unused gems in your bundler directory

bundle config

Retrieve or set a configuration value

bundle console

Opens an IRB session with the bundle pre-loaded

bundle init

Generates a Gemfile into the current working directory

bundle update

Update the current environment

bundle show

Shows all gems that are part of the bundle, or the path to a given gem

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 'images/show'

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

Automagically create all the routes for a RESTful resource

# config/routes.rb
resources :images 

HTTP Verb	Path	Controller#Action	Used for
GET	/images	images#index	display a list of all images
GET	/images_new	images#new	return an HTML form for creating a new image
POST	/images	images#create	create a new image
GET	/images/:id	images#show	display a specific image
GET	/images/:id/edit	images#edit	return an HTML form for editing a image
PATCH/PUT	/images/:id	images#update	update a specific image
DELETE	/images/:id	images#destroy	delete a specific image

Create resources for only certain actions

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

# On the flip side, you can create a resource with exceptions 
resources :images, :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/images', this file will be 
#   automatically rendered when you call localhost:3000/images/about
get 'images/about', to: 'images#about'

Controllers

Generate a new controller

Note: Name controllers in Pascal case and pluralize

rails g controller Images

Generate a new controller with default actions, routes and views

rails g controller Images index show

Models

Generate a model and create a migration for the table

Note: Name models in Pascal case and singular

rails g model Image

Generate a model and create a migration with table columns

rails g model Image path:string caption:text

The migration automatically created for the above command:

class CreateImages < ActiveRecord::Migration
  def change
    create_table :images do |t|
      t.string :path
      t.text :caption
 
      t.timestamps null: false
    end
  end
end

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 AddDateTakenToImages date_taken:datetime

The above creates the following migration:

class AddDateTakenToImages < ActiveRecord::Migration[5.0]
  def change
    add_column :images, :date_taken, :datetime
  end
end

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

rails g migration AddDateTakenToImages date_taken:datetime:index

The above command generates the following migration:

class AddDateTakenToImages < ActiveRecord::Migration[5.0]
  def change
    add_column :images, :date_taken, :datetime
    add_index :images, :date_taken
  end
end

The opposite goes for migration names following the format: RemoveXXXFromYYY

rails g migration RemoveDateTakenFromImages date_taken:datetime

The above generates the following migration:

class RemoveDateTakenFromImages < ActiveRecord::Migration[5.0]
  def change
    remove_column :images, :date_taken, :datetime
  end
end

Scaffolding

Scaffolding is great for prototype applications:

rails g scaffold Image path:string caption:text
rake db:migrate

Path Helpers

Creating a path helper for a route

# Creating a path helper for a route
get '/images/:id', to: 'images#show', as: 'image'

# app/controllers/images_controller.rb
@image = Image.find(17)

# View for the action
<%= link_to 'Image Record', image_path(@image) %>

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

# config/routes.rb
resources :images

HTTP Verb	Path	Controller#Action	Named Helper
GET	/images	images#index	images_path
GET	/images/new	images#new	new_image_path
POST	/images	images#create	images_path
GET	/images/:id	images#show	image_path(:id)
GET	/images/:id/edit	images#edit	edit_image_path(:id)
PATCH/PUT	/images/:id	images#update	image_path(:id)
DELETE	/images/:id	images#destroy	image_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>

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/images_controller.rb
def new
  @image = Image.new
end

# ERB view
<%= form_for @image, 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="/images/create" method="post" class="nifty_form">
  <input id="images_path" name="image[path]" type="text" />
  <textarea id="images_caption" name="image[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>

Validation Helpers

When you create a Web site or Web application with RoR, you should make sure that you input data in a form that Rails recognizes and can use.

• validates_acceptance_of
• validates_inclusion_of
• validates_associated
• validates_length_of
• validates_confirmation_of
• validates_numericality_of
• validates_each
• validates_presence_of
• validates_exclusion_of
• validates_size_of
• validates_format_of
• validates_uniqueness_of

Iterators and Methods for RoR

When you want to travel through a database you created with RoR, using iterators is helpful:

Iterator/Method	Result
[1, 2, 3].each { }	[1, 2, 3]
[1, nil, nil, 2, 3, nil].compact { }	[1, 2, 3]
[1, 2, 3].delete_if {	x
[1, 2, 3].collect {	x
[1, 2, 3].find_all {	x
[1, 2, 3].reject {	x
[2, 5, 1, 0, 7].sort	[0, 1, 2, 5, 7]
[2, 5, 1, 0, 7].max	7
[1, [2, 3]].flatten	[1, 2, 3]
[1, 2, 3].empty?	false
[].empty?	true
[0, 5, 9].length	3
[1, 2, 3].include?(2)	true
[1, 2, 3].include?(16)	false
[1, 2, 3].reverse	[3, 2, 1]