Ruby code explainers

module UniqueJob
  extend ActiveSupport::Concern
 
  class_methods do

class OrderMailerPreview < ActionMailer::Preview
  def confirmation
    OrderMailer.confirmation(sample_order)
  end

def render_table(rows)
  return "(no data)" if rows.empty?
 
  columns = rows.flat_map(&:keys).uniq

class ApplicationController < ActionController::Base
  ALLOWED_REDIRECT_HOSTS = [nil, ENV.fetch("APP_HOST", "app.example.com")].freeze
 
  def store_return_to(location = request.fullpath)

require 'set'
 
class DirectoryWatcher
  def initialize(path, pattern: '**/*', interval: 1.0)

class HashDiff
  Change = Struct.new(:from, :to)
 
  def self.call(before, after)

module CreditCard
  module_function
 
  def valid?(number)

class UserColor
  GOLDEN_RATIO_CONJUGATE = 0.618033988749895
 
  def initialize(username)

namespace :counter_cache do
  desc "Recalculate comments_count for posts after a backfill"
  task warm_post_comments: :environment do
    scope = Post.where(comments_count: nil).or(Post.where("comments_count < 0"))

class ToastBroadcaster
  include ActionView::RecordIdentifier
 
  def self.broadcast_to(user, message:, type: :notice)

class TemplateInterpolator
  PLACEHOLDER = /\{\{\s*([\w.]+)\s*\}\}/
 
  def initialize(strict: false)

class KeyTransformer
  def self.camelize(data)
    new.camelize(data)
  end

module Paginatable
  extend ActiveSupport::Concern
 
  private

class Api::MessagesController < ApiController
  before_action :authenticate_api_key!
 
  rate_limit to: 100,

class Order < ApplicationRecord
  include AASM
 
  belongs_to :warehouse

require "timeout"
require "net/http"
 
class RemoteInventoryClient

require "base64"
require "json"
 
module Attachment

require "yaml"
 
class FrontMatter
  DELIMITER = /\A---\s*\n(.*?)\n---\s*\n?(.*)\z/m