Ruby code explainers

module SoftDeletable
  extend ActiveSupport::Concern
 
  included do

class Post < ApplicationRecord
  before_validation :generate_slug, on: :create
 
  validates :slug, presence: true, uniqueness: true

module TextAnalysis
  module_function
 
  WORD_PATTERN = /[\p{Alpha}']+/

module Fibonacci
  CACHE = Hash.new do |cache, n|
    cache[n] = cache[n - 1] + cache[n - 2]
  end

class EventEmitter
  def initialize
    @listeners = Hash.new { |hash, key| hash[key] = [] }
  end

require 'optparse'
require 'ostruct'
 
def parse_options(argv)

module Retryable
  class RetriesExhausted < StandardError; end
 
  RETRYABLE_ERRORS = [

class Throttle
  def initialize(interval)
    @interval = interval
    @mutex = Mutex.new

class Article < ApplicationRecord
  before_validation :generate_slug, on: :create
 
  validates :slug, presence: true, uniqueness: true,

class CheckoutService
  Result = Struct.new(:success?, :order, :error, keyword_init: true)
 
  def self.call(...)

class User < ApplicationRecord
  has_one_attached :avatar
 
  validate :acceptable_avatar

class Article < ApplicationRecord
  belongs_to :author
 
  default_scope { where(deleted_at: nil) }

class Employee < ApplicationRecord
  validates :name, presence: true
  validates :salary, numericality: { greater_than: 0 }
 

class ArticlesController < ApplicationController
  before_action :authenticate_user!
  before_action :set_article, only: %i[show edit update destroy]
  before_action :authorize_owner!, only: %i[edit update destroy]

class CreateCommentsWithCounterCache < ActiveRecord::Migration[7.1]
  def change
    create_table :posts do |t|
      t.string :title, null: false

class ProductCatalog
  def featured_products
    Rails.cache.fetch("catalog/featured_products", expires_in: 12.hours) do
      Product.where(featured: true)

class RegistrationForm
  include ActiveModel::Model
  include ActiveModel::Attributes
 

# Curry a multi-argument lambda so it can be applied one argument at a time.
add = ->(a, b, c) { a + b + c }
 
# Proc#curry returns a curried version that collects arguments incrementally.