Ruby on Rails code explainers

class Comment < ApplicationRecord
  belongs_to :post
  belongs_to :author, class_name: "User"
 

class ReportBatcher
  BATCH_SIZE = 500
 
  def initialize(account)

class Comment < ApplicationRecord
  belongs_to :commentable, polymorphic: true, counter_cache: true
  belongs_to :author, class_name: "User"
 

class SessionsController < ApplicationController
  MAX_ATTEMPTS = 5
  THROTTLE_WINDOW = 15.minutes
 

class ProductsController < ApplicationController
  def index
    @products = Product
      .includes(:category, :brand)

class HostnameValidator < ActiveModel::EachValidator
  MAX_LENGTH = 253
  LABEL = /\A(?!-)[a-z0-9-]{1,63}(?<!-)\z/i
 

class PaymentsController < ApplicationController
  before_action :require_idempotency_key
 
  def create

class Survey < ApplicationRecord
  has_many :questions, dependent: :destroy
  has_many :respondents, dependent: :nullify
 

class OrderConfirmationJob < ApplicationJob
  queue_as :mailers
 
  retry_on Net::OpenTimeout, wait: :polynomially_longer, attempts: 5

module SoftDeletable
  extend ActiveSupport::Concern
 
  included do

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

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