Ruby on Rails

https://guides.rubyonrails.org/v8.0/
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### Implement Rails::Server#start

Source: https://guides.rubyonrails.org/v8.0/initialization.html

Defines the server startup sequence, including signal trapping, directory creation, and logger setup.

```ruby
module Rails
  class Server < ::Rackup::Server
    def start(after_stop_callback = nil)
      trap(:INT) { exit }
      create_tmp_directories
      setup_dev_caching
      log_to_stdout if options[:log_stdout]

      super()
      # ...
    end

    private
      def setup_dev_caching
        if options[:environment] == "development"
          Rails::DevCaching.enable_by_argument(options[:caching])
        end
      end

      def create_tmp_directories
        %w(cache pids sockets).each do |dir_to_make|
          FileUtils.mkdir_p(File.join(Rails.root, "tmp", dir_to_make))
        end
      end

      def log_to_stdout
        wrapped_app # touch the app so the logger is set up

        console = ActiveSupport::Logger.new(STDOUT)
        console.formatter = Rails.logger.formatter
        console.level = Rails.logger.level

        unless ActiveSupport::Logger.logger_outputs_to?(Rails.logger, STDERR, STDOUT)
          Rails.logger.broadcast_to(console)
        end
      end
  end
end
```

--------------------------------

### Kamal Initial Server Setup (Shell)

Source: https://guides.rubyonrails.org/v8.0/getting_started.html

This command initiates the setup process for deploying a Rails application using Kamal. It configures the production server environment, including installing necessary dependencies and preparing the server for the application.

```shell
$ bin/kamal setup
```

--------------------------------

### Solid Cable Adapter Setup

Source: https://guides.rubyonrails.org/v8.0/action_cable_overview.html

Instructions for installing and configuring the Solid Cable adapter, which uses Active Record and requires manual database configuration.

```APIDOC
## Solid Cable Adapter Setup

### Description

The Solid Cable adapter is a database-backed solution that uses Active Record. It has been tested with MySQL, SQLite, and PostgreSQL. Running `bin/rails solid_cable:install` will automatically set up `config/cable.yml` and create `db/cable_schema.rb`. After that, you must manually update `config/database.yml`, adjusting it based on your database.

### Method

N/A (Installation and Configuration)

### Endpoint

N/A

### Parameters

N/A

### Request Example

N/A

### Response

N/A
```

--------------------------------

### Rails Script Command Examples

Source: https://guides.rubyonrails.org/v8.0/2_2_release_notes.html

Illustrates various command-line scripts used in Rails development, such as starting the server with Thin, installing plugins with specific revisions, and accessing the Rails console with debugger support.

```Shell
script/server
script/plugin install <plugin> -r <revision>
script/console --debugger
```

--------------------------------

### Start Rails Server with Rack::Server

Source: https://guides.rubyonrails.org/v8.0/rails_on_rack.html

Demonstrates how bin/rails server creates and starts a Rack::Server object. This code is executed when starting the Rails development server.

```ruby
Rails::Server.new.tap do |server|
  require APP_PATH
  Dir.chdir(Rails.application.root)
  server.start
end

```

```ruby
class Server < ::Rack::Server
  def start
    # ...
    super
  end
end

```

--------------------------------

### Start Rails Server

Source: https://guides.rubyonrails.org/v8.0/command_line.html

Use `bin/rails server` to start the development server. Access your application at http://localhost:3000.

```bash
$ bin/rails server
=> Booting Puma...


```

--------------------------------

### Code Example Formatting

Source: https://guides.rubyonrails.org/v8.0/api_documentation_guidelines.html

Demonstrates how to format code examples, including indentation, Rails conventions, and inline comments with results.

```APIDOC
## Example Code

Choose meaningful examples that depict and cover the basics as well as interesting points or gotchas.
For proper rendering, indent code by two spaces from the left margin. The examples themselves should use Rails coding conventions.
Short docs do not need an explicit "Examples" label to introduce snippets; they just follow paragraphs:
```ruby
# Converts a collection of elements into a formatted string by
# calling +to_s+ on all elements and joining them.
#
#   Blog.all.to_fs # => "First PostSecond PostThird Post"
```

On the other hand, big chunks of structured documentation may have a separate "Examples" section:
```ruby
# ==== Examples
#
#   Person.exists?(5)
#   Person.exists?('5')
#   Person.exists?(name: "David")
#   Person.exists?(name: "David")
#   Person.exists?(["name LIKE ?", "%#{query}%"])
```

The results of expressions follow them and are introduced by "# => ", vertically aligned:
```ruby
# For checking if an integer is even or odd.
#
#   1.even? # => false
#   1.odd?  # => true
#   2.even? # => true
#   2.odd?  # => false
```

If a line is too long, the comment may be placed on the next line:
```ruby
#   label(:article, :title)
#   # => <label for="article_title">Title</label>
#
#   label(:article, :title, "A short title")
#   # => <label for="article_title">A short title</label>
#
#   label(:article, :title, "A short title", class: "title_label")
#   # => <label for="article_title" class="title_label">A short title</label>
```

Avoid using any printing methods like `puts` or `p` for that purpose.
On the other hand, regular comments do not use an arrow:
```ruby
#   polymorphic_url(record)  # same as comment_url(record)
```
```

--------------------------------

### Start the Rails Server

Source: https://guides.rubyonrails.org/v8.0/asset_pipeline.html

Run the `bin/rails server` command to start the Rails development server.

```bash
$ bin/rails server
```

--------------------------------

### Generate HTML Rails Guides in a Specific Language

Source: https://guides.rubyonrails.org/v8.0/contributing_to_ruby_on_rails.html

This command generates the Rails guides in HTML format for a specified language. It requires installing dependencies and navigating to the guides directory. Ensure you have the necessary gems installed.

```bash
$ BUNDLE_ONLY=default:doc bundle install
$ cd guides/
$ BUNDLE_ONLY=default:doc bundle exec rake guides:generate:html GUIDES_LANGUAGE=it-IT
```

--------------------------------

### Create Rails Application Template with Devise Setup (Ruby)

Source: https://guides.rubyonrails.org/v8.0/generators.html

This Ruby script defines an application template that automates the setup of the Devise gem in a new Rails application. It interactively asks the user if they want to install Devise, prompts for the user model name, adds the gem to the Gemfile, runs Devise generators, performs database migrations, and makes an initial Git commit.

```ruby
# template.rb
if yes?("Would you like to install Devise?")
  gem "devise"
  devise_model = ask("What would you like the user model to be called?", default: "User")
end

after_bundle do
  if devise_model
    generate "devise:install"
    generate "devise", devise_model
    rails_command "db:migrate"
  end

  git add: ".", commit: %(-m 'Initial commit')
end
```

--------------------------------

### Install Dependencies on Ubuntu

Source: https://guides.rubyonrails.org/v8.0/development_dependencies_install.html

Commands to install required system packages, Node.js, and Yarn on Ubuntu-based systems.

```bash
sudo apt-get update
sudo apt-get install sqlite3 libsqlite3-dev mysql-server libmysqlclient-dev postgresql postgresql-client postgresql-contrib libpq-dev redis-server memcached imagemagick ffmpeg mupdf mupdf-tools libxml2-dev libvips42 poppler-utils libyaml-dev libffi-dev
sudo mkdir -p /etc/apt/keyrings
curl --fail --silent --show-error --location https://deb.nodesource.com/gpgkey/nodesource-repo.gpg.key | sudo gpg --dearmor -o /etc/apt/keyrings/nodesource.gpg
echo "deb [signed-by=/etc/apt/keyrings/nodesource.gpg] https://deb.nodesource.com/node_20.x nodistro main" | sudo tee /etc/apt/sources.list.d/nodesource.list
sudo apt-get update
sudo apt-get install -y nodejs
sudo npm install --global yarn
```

--------------------------------

### Install and Migrate Action Mailbox

Source: https://guides.rubyonrails.org/v8.0/action_mailbox_basics.html

Commands to install the Action Mailbox framework and run the necessary database migrations to store inbound emails.

```bash
bin/rails action_mailbox:install
bin/rails db:migrate
```

--------------------------------

### Manage Services on macOS with Homebrew

Source: https://guides.rubyonrails.org/v8.0/development_dependencies_install.html

Commands to install, list, and start system services required for Rails development using Homebrew.

```bash
brew bundle
brew services list
brew services start mysql
```

--------------------------------

### Generate Rails Guides Locally

Source: https://guides.rubyonrails.org/v8.0/2_2_release_notes.html

This command generates the Rails Guides documentation locally within your application. The generated guides are placed in `Rails.root/doc/guides` and can be accessed by opening `Rails.root/doc/guides/index.html` in a web browser.

```bash
$ rake doc:guides
```

--------------------------------

### Ruby Option Section Style Example

Source: https://guides.rubyonrails.org/v8.0/api_documentation_guidelines.html

Presents an alternative documentation style for providing additional details and examples, particularly for options. This style uses a section header like '==== Options' followed by detailed explanations and code examples for each option.

```Ruby
# ==== Options
#
# [+:expires_at+]
#   The datetime at which the message expires. After this datetime,
#   verification of the message will fail.
#
#     message = encryptor.encrypt_and_sign("hello", expires_at: Time.now.tomorrow)
#     encryptor.decrypt_and_verify(message) # => "hello"
#     # 24 hours later...
#     encryptor.decrypt_and_verify(message) # => nil
```

--------------------------------

### Install Ruby on Windows via WSL

Source: https://guides.rubyonrails.org/v8.0/install_ruby_on_rails.html

Sets up the Windows Subsystem for Linux (WSL) and installs the required Ruby development environment within the Ubuntu distribution.

```bash
wsl --install --distribution Ubuntu-24.04
sudo apt update
sudo apt install build-essential rustc libssl-dev libyaml-dev zlib1g-dev libgmp-dev
curl https://mise.run | sh
echo 'eval "$(~/.local/bin/mise activate bash)"' >> ~/.bashrc
source ~/.bashrc
mise use -g ruby@3
```

--------------------------------

### Install Rails 3 with Gem

Source: https://guides.rubyonrails.org/v8.0/3_0_release_notes.html

Command to install the Ruby on Rails version 3.0 using the RubyGems package manager. Use sudo if necessary for system-wide installation.

```bash
# Use sudo if your setup requires it
$ gem install rails
```

--------------------------------

### Creating an Article Record

Source: https://guides.rubyonrails.org/v8.0/action_view_overview.html

Example of creating an article record for demonstration purposes.

```ruby
Article.create(body: "Partial Layouts are cool!")
```

--------------------------------

### Install Ruby on Ubuntu

Source: https://guides.rubyonrails.org/v8.0/install_ruby_on_rails.html

Installs necessary build dependencies and the Mise version manager on Ubuntu to support Ruby development.

```bash
sudo apt update
sudo apt install build-essential rustc libssl-dev libyaml-dev zlib1g-dev libgmp-dev git
curl https://mise.run | sh
echo 'eval "$(~/.local/bin/mise activate)"' >> ~/.bashrc
source ~/.bashrc
mise use -g ruby@3
```

--------------------------------

### Ruby Asset Tag Helper Example (image_tag)

Source: https://guides.rubyonrails.org/v8.0/api_documentation_guidelines.html

Illustrates documenting framework behavior within the full Rails stack, using `ActionView::Helpers::AssetTagHelper#image_tag` as an example. It shows how the output of `image_tag` can differ when considering the Asset Pipeline, emphasizing that documentation should reflect the user's experience with the complete framework.

```Ruby
# image_tag("icon.png")
#   # => <img src="/assets/icon.png" />
```

--------------------------------

### Install Dependencies on Fedora or CentOS

Source: https://guides.rubyonrails.org/v8.0/development_dependencies_install.html

Commands to install required system packages, Node.js, and Yarn on Fedora or CentOS systems.

```bash
sudo dnf install sqlite-devel sqlite-libs mysql-server mysql-devel postgresql-server postgresql-devel redis memcached ImageMagick ffmpeg mupdf libxml2-devel vips poppler-utils
sudo dnf install https://rpm.nodesource.com/pub_20/nodistro/repo/nodesource-release-nodistro-1.noarch.rpm -y
sudo dnf install nodejs -y --setopt=nodesource-nodejs.module_hotfixes=1
sudo npm install --global yarn
```

--------------------------------

### Define Initial Models for `includes` Example

Source: https://guides.rubyonrails.org/v8.0/association_basics.html

These are the base model definitions used in the `includes` example to demonstrate second-order association eager loading.

```ruby
class Supplier < ApplicationRecord
  has_one :account
end

class Account < ApplicationRecord
  belongs_to :supplier
  belongs_to :representative
end

class Representative < ApplicationRecord
  has_many :accounts
end
```

--------------------------------

### Generate Rails Guides

Source: https://guides.rubyonrails.org/v8.0/ruby_on_rails_guides_guidelines.html

Commands to generate HTML documentation for Rails guides. Supports full generation, selective file processing via the ONLY variable, and language localization.

```shell
bundle exec rake guides:generate
bundle exec rake guides:generate:html
touch my_guide.md
bundle exec rake guides:generate ONLY=my_guide
bundle exec rake guides:generate GUIDES_LANGUAGE=es
```

--------------------------------

### Install Active Storage

Source: https://guides.rubyonrails.org/v8.0/active_storage_overview.html

Run these commands to generate the necessary database tables for Active Storage.

```bash
$ bin/rails active_storage:install
$ bin/rails db:migrate
```

--------------------------------

### DRY controller tests with setup and teardown

Source: https://guides.rubyonrails.org/v8.0/testing.html

Uses setup and teardown callbacks to share article fixtures and manage cache across multiple tests.

```ruby
require "test_helper"

class ArticlesControllerTest < ActionDispatch::IntegrationTest
  # called before every single test
  setup do
    @article = articles(:one)
  end

  # called after every single test
  teardown do
    # when controller is using cache it may be a good idea to reset it afterwards
    Rails.cache.clear
  end

  test "should show article" do
    # Reuse the @article instance variable from setup
    get article_url(@article)
    assert_response :success
  end

  test "should destroy article" do
    assert_difference("Article.count", -1) do
      delete article_url(@article)
    end

    assert_redirected_to articles_path
  end

  test "should update article" do
    patch article_url(@article), params: { article: { title: "updated" } }

    assert_redirected_to article_path(@article)
    # Reload association to fetch updated data and assert that title is updated.
    @article.reload
    assert_equal "updated", @article.title
  end
end

```

--------------------------------

### Action Mailbox Example with Callbacks and Processing

Source: https://guides.rubyonrails.org/v8.0/action_mailbox_basics.html

An example Action Mailbox demonstrating the use of `before_processing` callbacks to validate conditions before email processing. It shows how to bounce emails using `bounced_with` and how to record email data into Active Record models or trigger Action Mailer.

```Ruby
# Example of a mailbox processing incoming emails
class ForwardsMailbox < ApplicationMailbox
  before_processing :ensure_user_has_projects

  def process
    record_forward
  end

  private

  def ensure_user_has_projects
    # Check if the 'forwarder' (user) has any projects
    unless forwarder.projects.any?
      bounced_with :no_projects_for_forwarder
    end
  end

  def record_forward
    # Create an Active Record model using email subject and body
    Project.create!(
      user: forwarder,
      subject: mail.subject,
      body: mail.decoded
    )
  end

  def forwarder
    # Find the user associated with the sender's email address
    User.find_by(email: mail.from)
  end
end

```

--------------------------------

### Implement Rackup::Server#start

Source: https://guides.rubyonrails.org/v8.0/initialization.html

Handles server configuration, PID management, and the final execution of the Rack application.

```ruby
module Rackup
  class Server
    def start(&block)
      if options[:warn]
        $-w = true
      end

      if includes = options[:include]
        $LOAD_PATH.unshift(*includes)
      end

      Array(options[:require]).each do |library|
        require library
      end

      if options[:debug]
        $DEBUG = true
        require "pp"
        p options[:server]
        pp wrapped_app
        pp app
      end

      check_pid! if options[:pid]

      # Touch the wrapped app, so that the config.ru is loaded before
      # daemonization (i.e. before chdir, etc).
      handle_profiling(options[:heapfile], options[:profile_mode], options[:profile_file]) do
        wrapped_app
      end

      daemonize_app if options[:daemonize]

      write_pid if options[:pid]

      trap(:INT) do
        if server.respond_to?(:shutdown)
          server.shutdown
        else
          exit
        end
      end

      server.run(wrapped_app, **options, &block)
    end
  end
end
```

--------------------------------

### Verify Rails Installation in Dev Container

Source: https://guides.rubyonrails.org/v8.0/getting_started_with_devcontainer.html

This command verifies that the Rails framework is correctly installed within the development container environment. It outputs the installed Rails version, confirming the setup is complete.

```bash
$ rails --version
Rails 8.0.0
```

--------------------------------

### Configure Solid Cache Sharding

Source: https://guides.rubyonrails.org/v8.0/caching_with_rails.html

Example `config/database.yml` demonstrating how to set up multiple cache shard databases for increased scalability.

```yaml
# config/database.yml
production:
  cache_shard1:
    database: cache1_production
    host: cache1-db
  cache_shard2:
    database: cache2_production
    host: cache2-db
  cache_shard3:
    database: cache3_production
    host: cache3-db

```

--------------------------------

### Find records in batches starting from a specific ID

Source: https://guides.rubyonrails.org/v8.0/active_record_querying.html

Combine `batch_size` and `start` options to retrieve records in batches, beginning from a specified ID. This example retrieves batches of 2500 records starting from ID 5000.

```ruby
Customer.find_in_batches(batch_size: 2500, start: 5000) do |customers|
  export.add_customers(customers)
end

```

--------------------------------

### Install Action Text with Rails Command

Source: https://guides.rubyonrails.org/v8.0/action_text_overview.html

Installs Action Text and its JavaScript dependencies, adds image processing gem, creates necessary database migrations, and sets up default view partials.

```bash
$ bin/rails action_text:install
```

--------------------------------

### Install Rails Gem Dependencies

Source: https://guides.rubyonrails.org/v8.0/contributing_to_ruby_on_rails.html

Install the necessary Ruby gems for the Rails project using Bundler. This command should be run after cloning the repository and before starting development.

```bash
$ bundle install
```

--------------------------------

### Automating Rails Application Setup with Templates

Source: https://guides.rubyonrails.org/v8.0/generators.html

Demonstrates a typical template script that scaffolds a model, configures routes, runs migrations, and initializes a git repository.

```ruby
generate(:scaffold, "person name:string")
route "root to: 'people#index'"
rails_command("db:migrate")

after_bundle do
  git :init
  git add: "."
  git commit: %Q{ -m 'Initial commit' }
end
```

--------------------------------

### Get Beginning of Minute for DateTime

Source: https://guides.rubyonrails.org/v8.0/active_support_core_extensions.html

Use `beginning_of_minute` to get a timestamp at the start of the current minute (hh:mm:00). This method is available for `DateTime` and `Time` objects.

```ruby
date = DateTime.new(2010, 6, 7, 19, 55, 25)
date.beginning_of_minute # => Mon Jun 07 19:55:00 +0200 2010
```

--------------------------------

### Configure Bundler and Bootsnap in config/boot.rb

Source: https://guides.rubyonrails.org/v8.0/initialization.html

Sets up the Gemfile path and initializes Bundler and Bootsnap for dependency management and boot optimization.

```ruby
ENV["BUNDLE_GEMFILE"] ||= File.expand_path("../Gemfile", __dir__)

require "bundler/setup" # Set up gems listed in the Gemfile.
require "bootsnap/setup" # Speed up boot time by caching expensive operations.
```

--------------------------------

### Get All Parent Modules with module_parents

Source: https://guides.rubyonrails.org/v8.0/active_support_core_extensions.html

The `module_parents` method returns an array of all containing modules, starting from the immediate parent up to `Object`.

```ruby
module X
  module Y
    module Z
    end
  end
end
M = X::Y::Z

X::Y::Z.module_parents # => [X::Y, X, Object]
M.module_parents       # => [X::Y, X, Object]
```

--------------------------------

### Initialize Rackup Server

Source: https://guides.rubyonrails.org/v8.0/initialization.html

The initialize method sets up server options, either from provided arguments or by parsing ARGV.

```ruby
module Rackup
  class Server
    def initialize(options = nil)
      @ignore_options = []

      if options
        @use_default_options = false
        @options = options
        @app = options[:app] if options[:app]
      else
        @use_default_options = true
        @options = parse_options(ARGV)
      end
    end
  end
end
```

--------------------------------

### Set Up Testing Database for Plugin

Source: https://guides.rubyonrails.org/v8.0/plugins.html

Navigates to the dummy Rails application within the plugin's test directory and creates the testing database using 'bin/rails db:create'. This ensures the plugin can be tested in a realistic Rails environment.

```bash
cd test/dummy
bin/rails db:create
```

--------------------------------

### Define Basic Rails Routes

Source: https://guides.rubyonrails.org/v8.0/getting_started.html

Examples of mapping HTTP GET and POST requests to specific controller actions within the config/routes.rb file.

```ruby
Rails.application.routes.draw do
  get "/products", to: "products#index"
  post "/products", to: "products#create"
end
```

--------------------------------

### Manual data setup for render

Source: https://guides.rubyonrails.org/v8.0/layouts_and_rendering.html

Manually populates instance variables and sets a flash message before rendering the index template to avoid a redirect round trip.

```ruby
def index
  @books = Book.all
end

def show
  @book = Book.find_by(id: params[:id])
  if @book.nil?
    @books = Book.all
    flash.now[:alert] = "Your book was not found"
    render "index"
  end
end
```

--------------------------------

### Declare Disk Service

Source: https://guides.rubyonrails.org/v8.0/active_storage_overview.html

Example configuration for the local Disk storage service.

```yaml
local:
  service: Disk
  root: <%= Rails.root.join("storage") %>
```

--------------------------------

### Boot Application

Source: https://guides.rubyonrails.org/v8.0/command_line.html

Use `bin/rails boot` to boot the application and then exit. This can be useful for testing the application's startup process.

```bash
bin/rails boot

```

--------------------------------

### Pluck distinct column values

Source: https://guides.rubyonrails.org/v8.0/active_record_querying.html

Use `pluck` with `distinct` to retrieve an array of unique values from a specified column. This is useful for getting a list of all possible statuses, for example.

```ruby
irb> Order.distinct.pluck(:status)
SELECT DISTINCT status FROM orders
=> ["shipped", "being_packed", "cancelled"]
```

--------------------------------

### Create Database Migrations

Source: https://guides.rubyonrails.org/v8.0/active_record_basics.html

Provides an example of a database-agnostic migration file to create a new table with various column types.

```ruby
class CreatePublications < ActiveRecord::Migration[8.0]
  def change
    create_table :publications do |t|
      t.string :title
      t.text :description
      t.references :publication_type
      t.references :publisher, polymorphic: true
      t.boolean :single_issue

      t.timestamps
    end
  end
end
```

--------------------------------

### Rake Command for Rails Gem Management

Source: https://guides.rubyonrails.org/v8.0/2_2_release_notes.html

Provides examples of Rake commands used for managing gem dependencies within a Rails application, including listing, installing, unpacking, and building gems and their dependencies.

```Shell
rake gems
rake gems:install
rake gems:unpack
rake gems:unpack:dependencies
rake gems:build
rake gems:refresh_specs
```

--------------------------------

### Initialize Rails Application Routes

Source: https://guides.rubyonrails.org/v8.0/i18n.html

Basic setup for a standard Rails application root route.

```ruby
Rails.application.routes.draw do
  root to: "home#index"
end
```

--------------------------------

### Ruby on Rails: Active Model API Lint Testing Setup

Source: https://guides.rubyonrails.org/v8.0/active_model_basics.html

This example demonstrates how to set up lint tests for an Active Model object by including `ActiveModel::Lint::Tests` in a test case. It shows the basic structure for testing API compliance.

```ruby
class Person
  include ActiveModel::API
end
```

```ruby
require "test_helper"

class PersonTest < ActiveSupport::TestCase
  include ActiveModel::Lint::Tests

  setup do
    @model = Person.new
  end
end
```

--------------------------------

### Handle file uploads in views and controllers

Source: https://guides.rubyonrails.org/v8.0/active_storage_overview.html

Example of a file field in a form and the corresponding controller parameter handling.

```erb
<%= form.file_field :avatar %>
```

```ruby
class SignupController < ApplicationController
  def create
    user = User.create!(user_params)
    session[:user_id] = user.id
    redirect_to root_path
  end

  private
    def user_params
      params.expect(user: [:email_address, :password, :avatar])
    end
end
```

--------------------------------

### Verify Ruby and Install Rails

Source: https://guides.rubyonrails.org/v8.0/install_ruby_on_rails.html

Verifies the current Ruby installation and installs the latest version of the Rails framework using the gem package manager.

```bash
ruby --version
gem install rails
rails --version
```

--------------------------------

### Start Rails Development Server

Source: https://guides.rubyonrails.org/v8.0/getting_started.html

This command boots the Puma web server within the application context. It ensures the correct version of Rails is used and provides a local URL to access the application.

```bash
bin/rails server
```

--------------------------------

### Connect via DATABASE_URL environment variable

Source: https://guides.rubyonrails.org/v8.0/configuring.html

Demonstrates connection behavior when config/database.yml is empty but DATABASE_URL is set.

```bash
$ cat config/database.yml

$ echo $DATABASE_URL
postgresql://localhost/my_database
```

--------------------------------

### Create a new Rails application

Source: https://guides.rubyonrails.org/v8.0/command_line.html

Initializes a new Rails project directory structure with default settings.

```bash
$ rails new my_app
     create
     create  README.md
     create  Rakefile
     create  config.ru
     create  .gitignore
     create  Gemfile
     create  app
     ...
     create  tmp/cache
     ...
        run  bundle install
```

--------------------------------

### Install and Update Bundler

Source: https://guides.rubyonrails.org/v8.0/ruby_on_rails_guides_guidelines.html

Commands to ensure the latest version of Bundler is installed or updated on the system.

```shell
gem install bundler
gem update bundler
```

--------------------------------

### Customize Solid Cache Store Options

Source: https://guides.rubyonrails.org/v8.0/caching_with_rails.html

Example `config/cache.yml` showing how to customize Solid Cache store options like `max_age` and `max_size`.

```yaml
default:
  store_options:
    # Cap age of oldest cache entry to fulfill retention policies
    max_age: <%= 60.days.to_i %>
    max_size: <%= 256.megabytes %>
    namespace: <%= Rails.env %>

```

--------------------------------

### Install Action Text for Rich Text Fields (Rails CLI)

Source: https://guides.rubyonrails.org/v8.0/getting_started.html

These commands install Action Text, a Rails feature for handling rich text content with embeds. The process involves running the Action Text installer, installing bundle dependencies, and migrating the database to add necessary tables. Restarting the Rails server is required to load the new features.

```bash
$ bin/rails action_text:install
$ bundle install
$ bin/rails db:migrate
```

--------------------------------

### Install importmap-rails Gem

Source: https://guides.rubyonrails.org/v8.0/working_with_javascript_in_rails.html

Manually install the importmap-rails gem into an existing Rails application to manage JavaScript dependencies.

```bash
$ bin/bundle add importmap-rails
$ bin/rails importmap:install
```

--------------------------------

### View Rails Server Output

Source: https://guides.rubyonrails.org/v8.0/getting_started.html

Example output from the Rails server startup process, indicating the server version, environment, and the local address where the application is listening.

```text
=> Booting Puma
=> Rails 8.0.0 application starting in development
=> Run `bin/rails server --help` for more startup options
Puma starting in single mode...
* Puma version: 6.4.3 (ruby 3.3.5-p100) ("The Eagle of Durango")
*  Min threads: 3
*  Max threads: 3
*  Environment: development
*          PID: 12345
* Listening on http://127.0.0.1:3000
* Listening on http://[::1]:3000
Use Ctrl-C to stop
```

--------------------------------

### Connect via config/database.yml

Source: https://guides.rubyonrails.org/v8.0/configuring.html

Demonstrates connection behavior when config/database.yml is populated and DATABASE_URL is unset.

```bash
$ cat config/database.yml
development:
  adapter: postgresql
  database: my_database
  host: localhost

$ echo $DATABASE_URL
```

--------------------------------

### Verify Yarn Installation

Source: https://guides.rubyonrails.org/v8.0/working_with_javascript_in_rails.html

Verify that Yarn, a JavaScript package manager, is installed correctly and accessible in your system's PATH.

```bash
$ yarn --version
```

--------------------------------

### Implement after_initialize and after_find Callbacks

Source: https://guides.rubyonrails.org/v8.0/active_record_callbacks.html

Shows how to hook into object instantiation and database retrieval events.

```ruby
class User < ApplicationRecord
  after_initialize do |user|
    Rails.logger.info("You have initialized an object!")
  end

  after_find do |user|
    Rails.logger.info("You have found an object!")
  end
end
```

```ruby
irb> User.new
You have initialized an object!
=> #<User id: nil>

irb> User.first
You have found an object!
You have initialized an object!
=> #<User id: 1>
```

--------------------------------

### Verify Node.js Installation

Source: https://guides.rubyonrails.org/v8.0/working_with_javascript_in_rails.html

Verify that Node.js is installed correctly and meets the minimum version requirement for JavaScript bundling in Rails.

```bash
$ node --version
```

--------------------------------

### Verify Bun Installation

Source: https://guides.rubyonrails.org/v8.0/working_with_javascript_in_rails.html

Verify that the Bun JavaScript runtime and bundler is installed correctly and accessible in your system's PATH.

```bash
$ bun --version
```

--------------------------------

### Parallel testing setup and teardown hooks

Source: https://guides.rubyonrails.org/v8.0/testing.html

Use parallelize_setup and parallelize_teardown to manage resources like databases when using process-based parallelization.

```ruby
class ActiveSupport::TestCase
  parallelize_setup do |worker|
    # setup databases
  end

  parallelize_teardown do |worker|
    # cleanup databases
  end

  parallelize(workers: :number_of_processors)
end
```

--------------------------------

### Start Standalone Cable Server

Source: https://guides.rubyonrails.org/v8.0/action_cable_overview.html

Command to launch the standalone Action Cable server using Puma on a specific port.

```bash
bundle exec puma -p 28080 cable/config.ru
```

--------------------------------

### Example Migration Output

Source: https://guides.rubyonrails.org/v8.0/active_record_migrations.html

Default output format for a migration creating a table and adding an index.

```text
==  CreateProducts: migrating =================================================
-- create_table(:products)
   -> 0.0028s
==  CreateProducts: migrated (0.0028s) ========================================
```

--------------------------------

### Calculate beginning and end of week

Source: https://guides.rubyonrails.org/v8.0/active_support_core_extensions.html

Returns the dates for the start and end of the week, with an optional argument to specify the starting day.

```ruby
d = Date.new(2010, 5, 8)     # => Sat, 08 May 2010
d.beginning_of_week          # => Mon, 03 May 2010
d.beginning_of_week(:sunday) # => Sun, 02 May 2010
d.end_of_week                # => Sun, 09 May 2010
d.end_of_week(:sunday)       # => Sat, 08 May 2010
```

--------------------------------

### Vulnerable Token Validation Example

Source: https://guides.rubyonrails.org/v8.0/security.html

An example of code susceptible to SQL injection via parameter manipulation when deep_munge is not active.

```ruby
unless params[:token].nil?
  user = User.find_by_token(params[:token])
  user.reset_password!
end
```

--------------------------------

### Configure Solid Cache with SQLite

Source: https://guides.rubyonrails.org/v8.0/caching_with_rails.html

Example configuration for `config/database.yml` to set up a separate SQLite database for Solid Cache, using a default connection as a base.

```yaml
production:
  primary:
    <<: *default
    database: storage/production.sqlite3
  cache:
    <<: *default
    database: storage/production_cache.sqlite3
    migrations_paths: db/cache_migrate

```

--------------------------------

### Install Webpacker Gem

Source: https://guides.rubyonrails.org/v8.0/upgrading_ruby_on_rails.html

Webpacker is the default JavaScript compiler for Rails 6. If upgrading an existing app, include it in your Gemfile and install it.

```ruby
gem "webpacker"
```

```bash
$ bin/rails webpacker:install
```

--------------------------------

### Example of Generating URL with Custom Parameter

Source: https://guides.rubyonrails.org/v8.0/routing.html

Shows how to generate a URL for a resource using its custom parameter (`identifier`) via the `edit_video_path` helper.

```ruby
irb> video = Video.find_by(identifier: "Roman-Holiday")
irb> edit_video_path(video)
=> "/videos/Roman-Holiday/edit"
```

--------------------------------

### Print Initializers

Source: https://guides.rubyonrails.org/v8.0/command_line.html

Use `bin/rails initializers` to list all defined initializers in the order they are invoked during application boot.

```bash
bin/rails initializers

```

--------------------------------

### Install Migrations for Specific Database - Rails CLI

Source: https://guides.rubyonrails.org/v8.0/engines.html

Installs migrations targeting a specific database, useful in multi-database Rails applications.

```bash
$ bin/rails railties:install:migrations DATABASE=animals

```

--------------------------------

### Rails View Code Example

Source: https://guides.rubyonrails.org/v8.0/command_line.html

This is an example of a generated view file. It displays content and uses an instance variable set in the controller.

```erb
<h1>A Greeting for You!</h1>
<p><%= @message %></p>


```

--------------------------------

### Run EXPLAIN with eager loading (MySQL/MariaDB)

Source: https://guides.rubyonrails.org/v8.0/active_record_querying.html

When using eager loading (`includes`), `explain` may execute multiple queries. This example shows the output for MySQL and MariaDB.

```ruby
Customer.where(id: 1).includes(:orders).explain
```

```sql
EXPLAIN SELECT `customers`.* FROM `customers`  WHERE `customers`.`id` = 1
+----+-------------+-----------+-------+---------------+ 
| id | select_type | table     | type  | possible_keys |
+----+-------------+-----------+-------+---------------+ 
|  1 | SIMPLE      | customers | const | PRIMARY       |
+----+-------------+-----------+-------+---------------+ 
+---------+---------+-------+------+-------+ 
| key     | key_len | ref   | rows | Extra |
+---------+---------+-------+------+-------+ 
| PRIMARY | 4       | const |    1 |       |
+---------+---------+-------+------+-------+

1 row in set (0.00 sec)

EXPLAIN SELECT `orders`.* FROM `orders`  WHERE `orders`.`customer_id` IN (1)
+----+-------------+--------+------+---------------+ 
| id | select_type | table  | type | possible_keys |
+----+-------------+--------+------+---------------+ 
|  1 | SIMPLE      | orders | ALL  | NULL          |
+----+-------------+--------+------+---------------+ 
+------+---------+------+------+-------------+ 
| key  | key_len | ref  | rows | Extra       |
+------+---------+------+------+-------------+ 
| NULL | NULL    | NULL |    1 | Using where |
+------+---------+------+------+-------------+


1 row in set (0.00 sec)
```

--------------------------------

### Rails Controller Code Example

Source: https://guides.rubyonrails.org/v8.0/command_line.html

This is an example of a generated controller file. It defines an action and sets an instance variable to be used in the view.

```ruby
class GreetingsController < ApplicationController
  def hello
    @message = "Hello, how are you today?"
  end
end


```

--------------------------------

### Puma Server Run Method Implementation

Source: https://guides.rubyonrails.org/v8.0/initialization.html

Handles the execution of the Puma server. It configures the server, sets up logging, creates a launcher instance, and starts the server, including graceful shutdown on interrupt.

```ruby
module Rack
  module Handler
    module Puma
      # ...
      def self.run(app, options = {})
        conf = self.config(app, options)

        log_writer = options.delete(:Silent) ? ::Puma::LogWriter.strings : ::Puma::LogWriter.stdio

        launcher = ::Puma::Launcher.new(conf, log_writer: log_writer, events: @events)

        yield launcher if block_given?
        begin
          launcher.run
        rescue Interrupt
          puts "* Gracefully stopping, waiting for requests to finish"
          launcher.stop
          puts "* Goodbye!"
        end
      end
      # ...
    end
  end
end

```

--------------------------------

### Integration Test GET Request

Source: https://guides.rubyonrails.org/v8.0/4_2_release_notes.html

Shows how to make a GET request in an integration test. The path must include a leading slash.

```ruby
test "list all posts" do
  get "/posts"
  assert_response :success
end
```

--------------------------------

### Create a book for an author manually

Source: https://guides.rubyonrails.org/v8.0/association_basics.html

Example of creating a record by explicitly setting the foreign key.

```ruby
@book = Book.create(author_id: @author.id, published_at: Time.now)
```

--------------------------------

### Install Migrations with Custom Path - Rails CLI

Source: https://guides.rubyonrails.org/v8.0/engines.html

Installs migrations from a specific engine, allowing for a custom path to store them within the application.

```bash
$ bin/rails railties:install:migrations MIGRATIONS_PATH=db_blourgh

```

--------------------------------

### Create New Rails Application

Source: https://guides.rubyonrails.org/v8.0/3_0_release_notes.html

Commands to initialize a new Rails application and navigate into the project directory.

```bash
rails new myapp
cd myapp
```

--------------------------------

### Configure Solid Cache with PostgreSQL/MySQL

Source: https://guides.rubyonrails.org/v8.0/caching_with_rails.html

Example configuration for `config/database.yml` using a primary database connection as a base for the Solid Cache database, suitable for PostgreSQL or MySQL.

```yaml
production:
  primary: &primary_production
    <<: *default
    database: app_production
    username: app
    password: <%= ENV["APP_DATABASE_PASSWORD"] %>
  cache:
    <<: *primary_production
    database: app_production_cache
    migrations_paths: db/cache_migrate

```

--------------------------------

### Rails Test Runner Examples

Source: https://guides.rubyonrails.org/v8.0/testing.html

Illustrates various ways to run tests, including single tests by line number, line ranges, and multiple files/directories.

```bash
Examples:
    You can run a single test by appending a line number to a filename:

        bin/rails test test/models/user_test.rb:27

    You can run multiple tests with in a line range by appending the line range to a filename:

        bin/rails test test/models/user_test.rb:10-20

    You can run multiple files and directories at the same time:

        bin/rails test test/controllers test/integration/login_test.rb

    By default test failures and errors are reported inline during a run.
```

--------------------------------

### Get Help for a Specific Rails Generator

Source: https://guides.rubyonrails.org/v8.0/command_line.html

You can get help for any generator by appending `--help` or `-h` to the command, similar to other Unix utilities.

```bash
$ bin/rails generate controller --help
Usage:
  bin/rails generate controller NAME [action action] [options]

...
...

Description:
    ...

    To create a controller within a module, specify the controller name as a path like 'parent_module/controller_name'.

    ...

Example:
    `bin/rails generate controller CreditCards open debit credit close`

    Credit card controller with URLs like /credit_cards/debit.
        Controller: app/controllers/credit_cards_controller.rb
        Test:       test/controllers/credit_cards_controller_test.rb
        Views:      app/views/credit_cards/debit.html.erb [...]
        Helper:     app/helpers/credit_cards_helper.rb


```

--------------------------------

### Verify Rails Installation Version

Source: https://guides.rubyonrails.org/v8.0/getting_started.html

Checks the currently installed version of the Rails framework. This ensures the environment meets the minimum requirement of version 8.0.0.

```bash
rails --version
```

--------------------------------

### Active Record: First or Create/Initialize Methods

Source: https://guides.rubyonrails.org/v8.0/3_2_release_notes.html

Introduces `first_or_create`, `first_or_create!`, and `first_or_initialize` for more explicit record finding and creation.

```APIDOC
## Active Record: First or Create/Initialize Methods

### Description
Provides methods to find a record by specified attributes or create a new one if it doesn't exist. `first_or_create!` raises an exception if creation fails validation.

### Method
GET/POST

### Endpoint
N/A (Active Record Method)

### Parameters
#### Find Parameters
- **first_name** (string) - Required - The first name to search for.

#### Create Parameters
- **last_name** (string) - Required - The last name to use when creating a new record.

### Request Example
```ruby
User.where(:first_name => "Scarlett").first_or_create!(:last_name => "Johansson")
```
```

--------------------------------

### Define Rackup::Server#app

Source: https://guides.rubyonrails.org/v8.0/initialization.html

Determines how to build the application based on provided options, either from a string or a configuration file.

```ruby
module Rackup
  class Server
    def app
      @app ||= options[:builder] ? build_app_from_string : build_app_and_options_from_config
    end

    # ...

    private
      def build_app_and_options_from_config
        if !::File.exist? options[:config]
          abort "configuration #{options[:config]} not found"
        end

        Rack::Builder.parse_file(self.options[:config])
      end

      def build_app_from_string
        Rack::Builder.new_from_string(self.options[:builder])
      end
  end
end
```

--------------------------------

### Install Rails Upgrade Plugin

Source: https://guides.rubyonrails.org/v8.0/3_0_release_notes.html

Installs the Rails Upgrade plugin via Git to assist in automating the upgrade process from older Rails versions.

```bash
ruby script/plugin install git://github.com/rails/rails_upgrade.git
```

--------------------------------

### View help for rails new

Source: https://guides.rubyonrails.org/v8.0/command_line.html

Displays available options and configuration flags for the rails new command.

```bash
$ rails new --help
```

--------------------------------

### Install All Railties Migrations - Rails CLI

Source: https://guides.rubyonrails.org/v8.0/engines.html

Copies migrations from all installed Railties (engines) into the application's `db/migrate` directory. Useful when managing multiple engines.

```bash
$ bin/rails railties:install:migrations

```
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