Ruby on Rails Cheat Sheet

We’ve been doing some Ruby on Rails development lately, in preparation for PagerTree 4, and we wanted to put together a Ruby on Rails Cheat sheet. This is a quick reference guide to common ruby on rails commands and usage.

Table of Contents:

  1. Ruby Syntax
    1. Hashes
    2. Safe Navigation Operator
    3. ERB
  2. Rails Commands
  3. Rake Commands
  4. Rails Framework
    1. Migration Data Types
    2. Controller Filters
    3. Model Callbacks
    4. Model Queries
    5. Fastest Check For Existence
    6. Application Configuration
    7. Application Secrets
  5. Useful Things
    1. Gems
    2. Frameworks
    3. Education

Ruby Syntax


Hashes were one of the most confusing things to me when first starting ruby (not because they are a new concept, but because I found the syntax very hard to read). In newer versions, syntax is very similar to JSON notification. Just know there are two versions of syntax, an older and newer one.

# old syntax
{ :one => "eins", :two => "zwei", :three => "drei" }

# new syntax
{ one: "eins", two: "zwei", three: "drei" } 

Also, you can have symbols as keys for hashes, and they do not lookup the same values as strings.

# notice the colon in front of our key
hash = {:one => "eins"} 

hash[:one] # results in "eins"

hash["one"] # results in nil

Safe Navigation Operator

Instead of checking for nil or undefined values, you can use the safe navigation operator. There’s a nice article here that goes into more depth of explanation.

# do this
if user&.email&.verified?

# instead of this
if user && &&


Evaluation and Output

Evaluation can be done with the <% %> syntax and output can be achieved with the <%= %> syntax.

<% if user.is_subscribed? %>
  You are subscribed to the <%= %> plan!
<% end %>


You can render partials like so:

<%= render partial: "shared/_nav_links" %>

Rails commands

Common rails commands. (Note: “rails g” stands for “rails generate”)

Command Description
rails g model user name:string age:integer account:references Generates model and migration files
rails g scaffold user name:string age:integer account:references Generates controller, model, migration, view, and test files. Also modifies config/routes.rb
rails g scaffold_controller user Generates controller and view files. Useful if you already have the model

Rake Commands

Common rake commands for database management and finding routes.

Command Description
rake routes View all routes in application (pair with grep command for some nifty searching)
rake db:seed Seed the database using the db/seeds.rb
rake db:migrate Run any pending migrations
rake db:rollback Rollback a database migration (add STEP=2 to remove multiple migrations)
rake db:drop db:create db:migrate Destroy the database, re-created it, and run migrations (useful for development)

Rails Framework

Migration Data Types

Migration data types. Here is the source and a stack overflow question I commonly reference.

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

Controller Filters

Filters are methods that are run “before”, “after” or “around” a controller action. See full action controller filters documentation for details.

Before filters are registered via the before_action and can halt the request cycle.

# controllers/application.rb
class ApplicationController < ActionController::Base
  before_action :require_login


  def require_login
    unless logged_in?
      flash[:error] = "You must be logged in to access this section"
      redirect_to new_login_url # halts request cycle

Models Callbacks

Gusto has a really nice article one best practices for model callbacks.

This table references the ruby on rails documentation for active record callbacks. Check out the full documentation for other special callbacks like after_touch.

New Record Updating Record Destroying Record
save save destroy
save! save! destroy!
create update_attribute  
create! update  
before_validation before_validation  
after_validation after_validation  
before_save before_save  
around_save around_save  
before_create before_update before_destroy
around_create around_update around_destroy
after_create after_update after_destroy
after_save after_save  
after_commit / after_rollback after_commit / after_rollback after_commit / after_rollback
# models/user.rb
class User < ApplicationRecord
  # Send a welcome email after they are created
  after_create :send_welcome_email

Model Queries

A couple of basic (and most commonly used) queries are below. You can find the full documentation here.

Command Example Description
Model.find(10) Find model by id
Model.find_by({ name: "Austin" }) Find models where conditions
Model.where("name = ?", params[:name]) Find models where condition
Model.where.not("name = ?", params[:name]) Find models where condition not true
Model.first Get the first model in the collection (ordered by primary key)
Model.last Get the lst model in the collection (ordered by primary key)
Model.order(:created_at) Order your results or query, :name) Select only specific fields
Model.limit(10).offset(20) Limit and offset (great for pagination)

Fastest Check For Existence

Additionally, you are likely to want to check for an existence of a condition many times. There are many ways to do this, namely present?, any?, empty?, and exists? but the exists? method will be the fastest. This semaphore article explains nicely why exists? is the fastest method for checking if one of a query exists.


Application Configuration

Application configuration should be located in config/application.rb with specific environment configurations in config/environments/. Don’t put sensitive data in your configuration files, that’s what the secrets are for. You can access configurations in your application code with the following:


Application Secrets

Application secrets are just that, secret (think API keys). You can edit the secrets file using the following commands rails credentials:edit --environment=env_name. This will create files in the config/credentials/ folder. You’ll get two files:

  1. environment.yml.enc - This is your secrets encrypted - This can be put this into git
  2. environment.key - This contains the key that encrypts the file - DO NOT put this into git.

Additionally, when deploying, the key inside the environment.key file will need to be placed into the RAILS_MASTER_KEY environment variable. You can then access secrets in your rails code like so:


Useful Things

A short list of gems, frameworks and education materials that I have found useful in my Rails journey.


  • Acts as Tenant - Easy multi-tenancy for rails database models.
  • Administrate - Rails engine for flexible admin dashboard.
  • Devise - Flexible authentication system.
  • Devise Masquerade - Provides “Login As” another user functionality for Devise.
  • Faker - Generate fake data like names, addresses, and phone numbers. Great for test data.
  • Hash Id - Expose a hashid instead of primary id to your users.
  • Local Time - Display friendly client side local time.
  • Lockbox - Encryption for database fields (model attributes).
  • Pagy - Gold standard pagination gem.
  • Rack Attack - Rack middleware (before Rails) for blocking & throttling.
  • Recaptcha - A rails Google Recaptcha plugin - You’ll want this one especially for public facing forms to stop bot crawlers.
  • StimulusJS - A tiny framework for sprinkles of Javascript for your front end.
  • Sequenced - Generate scoped ids (ex: per tenant ids for models, aka friendly id).
  • Sidekiq - Redis backed background processing for jobs.
  • Sidekiq Cron - A scheduler for Sidekiq (think running weekly email reports).
  • Turbolinks - Makes web app feels faster (like single page application).


  • Jumpstart Rails - A SaaS Framework already supporting login, payment (Stripe, Paypal, and Braintree) and multi-tenant setup.
  • tailwindcss - A utility first CSS framework. Seems a little verbose at first, but you’ll really learn to love it. Just by reading the code, you’ll know exactly what the screen will look like.


  • Go Rails - Ruby on Rails tutorials, guids, and screencasts.

I hope you find some value in this cheat sheet. There’s probably a lot I missed on here, so if you have something to add you can reach out to me on twitter and I will update the article with your suggestion.