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March 03, 2025 00:31
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Ruby on Rails Cheatsheet

A comprehensive cheat sheet covering essential Ruby on Rails commands, helpers, and best practices for efficient web development.

Rails Basics & Setup

Project Setup

rails new my_app - Create a new Rails application named ‘my_app’.

rails server or rails s - Start the Rails server.

Access it via http://localhost:3000.

rails console or rails c - Start the Rails console for interacting with the application.

rails db:create - Create the database defined in config/database.yml.

rails db:migrate - Run pending database migrations.

rails db:seed - Load the seed data from db/seeds.rb.

Generators

rails generate model ModelName attribute:type attribute2:type2 ... - Generate a model with specified attributes and types.

Example: rails generate model Product name:string price:decimal

rails generate controller ControllerName action1 action2 ... - Generate a controller with specified actions.

Example: rails generate controller Products index show new create edit update destroy

rails generate migration AddColumnToTable column:type - Generate a migration to add a column to a table.

Example: rails generate migration AddPriceToProducts price:decimal

rails generate resource ResourceName attribute:type ... - Generate a model, controller, and routes for a resource.

Example: rails generate resource Product name:string price:decimal

Basic Commands

rails routes - List all defined routes in the application.

rails test - Run all tests.

rails assets:precompile - Precompile assets for production.

Models & Database

ActiveRecord Basics

Model.all - Retrieve all records from the table.

Model.find(id) - Find a record by its ID.

Model.new(attributes) - Create a new model instance.

model.save - Save the model instance to the database.

model.update(attributes) - Update the attributes of the model instance.

model.destroy - Delete the model instance from the database.

Associations

has_one

A model has one of another model. Example: has_one :profile

belongs_to

A model belongs to another model. Example: belongs_to :user

has_many

A model has many of another model. Example: has_many :comments

has_many :through

A model has many of another model through an association. Example: has_many :appointments, through: :physician

Validations

validates :attribute, presence: true - Ensures the attribute is present.

validates :attribute, uniqueness: true - Ensures the attribute is unique.

validates :attribute, length: { minimum: 5, maximum: 20 } - Validates the length of the attribute.

validates :attribute, format: { with: /regex/ } - Validates the format of the attribute using a regular expression.

validates :attribute, numericality: true - Ensures the attribute is a number.

Controllers & Views

Controller Actions

index - Display a list of all records.

show - Display a specific record.

new - Display a form to create a new record.

create - Create a new record.

edit - Display a form to edit an existing record.

update - Update an existing record.

destroy - Delete a record.

Views & Templates

ERB (Embedded Ruby) templates are used to generate HTML views.

<%= @variable %> - Output the value of a variable.

<% code %> - Execute Ruby code.

<%= link_to 'Link Text', path %> - Create a link to a specified path.

<%= form_with(model: @model) do |form| %> ... <% end %> - Create a form for a model.

Layouts & Partials

Layouts provide a consistent look and feel across multiple pages.

Partials are reusable view templates.

<%= render 'partial_name' %> - Render a partial.

Use yield in layouts to insert content from views.

Routing & Assets

Routes

get 'path', to: 'controller#action' - Define a GET route.

post 'path', to: 'controller#action' - Define a POST route.

resource :resource_name - Define RESTful routes for a resource.

resources :resource_name - Define multiple RESTful routes for a resource.

root 'controller#action' - Define the root route.

Asset Pipeline

The asset pipeline manages CSS, JavaScript, and image assets.

Assets are located in the app/assets directory.

Use Sprockets directives (e.g., require, require_tree) to manage asset dependencies.

<%= asset_path('image.png') %> - Generate the path to an asset.

Helpers

number_to_currency(number) - Formats a number as currency.

date.strftime('%m/%d/%Y') - Format a date.

time_ago_in_words(time) - Show how long ago a time was.

pluralize(count, 'item') - Pluralize a word based on the count.