Ruby code explainers

ruby

class EditorHistory
  MAX_DEPTH = 100
 
  def initialize(initial = "")

How undo/redo history works in Ruby

undo-redo state-management immutability

Intermediate 9 steps

ruby

class Current < ActiveSupport::CurrentAttributes
  attribute :user, :request_id, :user_agent, :ip_address
 
  resets { Time.zone = nil }

Per-request audit trails with Current in Rails

thread-local-state auditing concerns

Intermediate 8 steps

ruby

class Category < ApplicationRecord
  belongs_to :parent, class_name: "Category", optional: true
  has_many :children,
           -> { order(:position) },

Modeling a self-referential category tree in Rails

self-referential-association recursion tree-structure

Intermediate 9 steps

ruby

module WifiQrCode
  ESCAPE_CHARS = /([\\;,:"])/.freeze
 
  AUTH_TYPES = {

Building a Wi-Fi QR code payload in Ruby

string-formatting validation escaping

Intermediate 9 steps

ruby

require "nokogiri"
require "open-uri"
require "set"

Extracting and normalizing links in Ruby

web-scraping url-parsing html-parsing

Intermediate 8 steps

ruby

require "yaml"
require "date"
 
class Money

Custom YAML serialization in Ruby

serialization yaml custom-encoding

Intermediate 7 steps

ruby

module Terminal
  module Color
    CODES = {
      black: 30, red: 31, green: 32, yellow: 33,

Building an ANSI color DSL in Ruby

metaprogramming monkey-patching ansi-escapes

Intermediate 9 steps

ruby

class ReportingQuery
  def initialize(scope = ApplicationRecord)
    @scope = scope
  end

Routing heavy reports to a read replica in Rails

read-replica database-roles query-object

Intermediate 6 steps

ruby

class WeatherLookup
  Result = Struct.new(:temperature, :conditions, keyword_init: true)
 
  class TimeoutError < StandardError; end

A resilient weather API service object in Rails

service-object http-client error-handling

Intermediate 7 steps

ruby

class Post < ApplicationRecord
  belongs_to :author, counter_cache: false
  has_many :comments, dependent: :destroy
end

A custom counter cache in Rails

counter-cache callbacks associations

Intermediate 7 steps

ruby

namespace :active_storage do
  desc "Purge blobs that have been unattached for more than 48 hours"
  task purge_stale: :environment do
    cutoff = 48.hours.ago

A Rake task to purge stale Active Storage blobs in Rails

rake active-storage batch-processing

Intermediate 8 steps

ruby

class Article < ApplicationRecord
  belongs_to :author
  has_many :taggings, dependent: :destroy
  has_many :tags, through: :taggings

Keeping a search index fresh in Rails

callbacks background-jobs debounce

Intermediate 9 steps

ruby

require "base64"
 
module Auth
  module BasicCredentials

Parsing HTTP Basic Auth headers in Ruby

parsing authentication base64

Intermediate 6 steps

ruby

class WeightedMovingAverageForecaster
  DEFAULT_WINDOW = 5
 
  def initialize(window: DEFAULT_WINDOW, weights: nil)

A weighted moving average forecaster in Ruby

forecasting weighted-average normalization

Intermediate 8 steps

ruby

class ApplicationController < ActionController::Base
  INACTIVITY_TIMEOUT = 30.minutes
 
  before_action :expire_stale_session

Idle session timeout in a Rails controller

authentication session-management before-action

Intermediate 6 steps

ruby

module Dotenv
  LINE = /\A\s*(?:export\s+)?([A-Za-z_][A-Za-z0-9_]*)\s*=\s*(.*?)\s*\z/
 
  module_function

Parsing a .env file in Ruby

parsing regular-expressions environment-variables

Intermediate 8 steps

ruby

class ChatChannel < ApplicationCable::Channel
  periodically :sweep_stale_typists, every: 3.seconds
 
  def subscribed

How a typing indicator works in Rails ActionCable

websockets presence cache-expiry

Intermediate 9 steps

ruby

class Author < ApplicationRecord
  has_many :posts
 
  scope :with_post_stats, -> {

Aggregating post stats in a Rails scope

scopes sql-aggregation left-join

Intermediate 8 steps