Rails Cheatsheet

Table of Contents

• New App
• Model
• Routes
• Controller
• DB Tasks
• Authentication (with Devise)

New App

$ rails new -T --database postgresql YOUR_APP_NAME

• -T : remove tests
• --database postgresql : use postgresql database
• YOUR_APP_NAME : replace it with your app name

Model

Create a model

$ rails g model *ObjectName* *attribute*:*type* *attribute*:*type*

• *ObjectName* : replace it by your model name (Capital letter & singular)
• *attribute* : replace it by the model attribute
• *type* : replace it by the attribute type :
  • string
  • text
  • integer
  • float
  • date
  • datetime
  • array
  • references

if references add has_many :object_names, params

params:

• dependent: :destroy: destroy the referent instance if this one is deleted

Migrate DB

$ rake db:migrate

Destroy a model

$ rails destroy model *object_name*

Add attributes to model

$ rails g migration Add*Attribute*To*ObjectName*s *attribute*:*type* *attribute*:*type*

• *Attribute* : CamelCase & singular
• *ObjectName*: Model Name plurial

Remove attributes from model

$ rails g migration Remove*Attribute*From*ObjectName*s

• *Attribute* : CamelCase & singular
• *ObjectName*: Model Name, CamelCase & plurial

Routes

Add to config/routes.rb

Rails.application.routes.draw do
  resources :*object_name*s
end

If you don't need all of them

Rails.application.routes.draw do
  resources :*object_name*s, only: [:create, :index, :destroy]
end

or

Rails.application.routes.draw do
  resources :*object_name*s, except: [:create, :index, :destroy]
end

Verify routes

$ rake routes

Controller

Create a controller

$ rails g controller *object_name*s

7 Instance methods

# app/controller/*object_name*s_controller.rb
class *ObjectName*sController < ApplicationController
  def index         # GET /*object_name*s
  end

  def show          # GET /*object_name*s/:id
  end

  def new           # GET /*object_name*s/new
  end

  def create        # POST /*object_name*s
  end

  def edit          # GET /*object_name*s/:id/edit
  end

  def update        # PATCH /*object_name*s/:id
  end

  def destroy       # DELETE /*object_name*s/:id
  end
end

Get all object instances

 def index
  @*object_name* = *ObjectName*.all
 end

Get 1 object instance

 def show
  @*object_name* = *ObjectName*.find(params[:id])
 end

Create & update

class *ObjectName*sController < ApplicationController
 def create
  @*object_name* = *ObjectName*.new(*object_name*_params)
  @*object_name*.save
  
  redirect_to *object_name*_path(@*object_name*)
 end

 def update
  @*object_name* = *ObjectName*.find(params[:id])
  @*object_name*.update(*object_name*_params)
  
  redirect_to *object_name*_path(@*object_name*)
 end

 private

 def *object_name*_params
  params.require(:*object_name*).permit(:*attribute*, :*other_attribute*)
 end
end

Delete

class *ObjectName*sController < ApplicationController
  def destroy
    @*object_name* = *ObjectName*.find(params[:id])
    @*object_name*.destroy

    redirect_to *object_name*s_path
  end
end

DB tasks

Drop the database (lose all your data!)

$ rake db:drop

Create the database with an empty schema

$ rake db:create

Run pending migrations on the database schema

$ rake db:migrate

Revert the last migration

$ rake db:rollback

Drop database + replay all migration

$ rake db:reset

Authentication (with Devise)

Add to Gemfile

gem 'devise'

Run in terminal

$ bundle install
$ rails generate devise:install

Add to config/environments/development.rb

config.action_mailer.default_url_options = { host: 'localhost', port: 3000 }

Add in your views (app/views/layouts/application.html.erb for example)

<p class="notice"><%= notice %></p>
<p class="alert"><%= alert %></p>

Add to config/initializers/devise.rb

config.mailer_sender = '[email protected]'

Create User Model

$ rails generate devise User

Migrate DB

$ rake db:migrate

Helpers

user_signed_in?
# => true / false

current_user
# => User instance / nil

Custom devise views

$ rails g devise:views

Protect your routes

Add to app/controllers/application_controller.rb

class ApplicationController < ActionController::Base
  before_action :authenticate_user!
end

To skip login for some page

class PagesController < ApplicationController
  skip_before_action :authenticate_user!, only: :home

  def home
  end
end