Ruby code explainers

ruby

require "shellwords"
require "open3"
 
module Backup

Building safe shell commands in Ruby

shell-out subprocess command-injection

Intermediate 7 steps

ruby

class UserAgentParser
  BROWSERS = [
    [/Edg\/([\d.]+)/, "Edge"],
    [/OPR\/([\d.]+)/, "Opera"],

Parsing user-agent strings in Ruby

regex pattern-matching lookup-tables

Intermediate 8 steps

ruby

class LogAggregator
  BUCKET_FORMAT = "%Y-%m-%dT%H:%M"
 
  def initialize(entries)

Bucketing log entries by the minute in Ruby

aggregation hashing enumerable

Intermediate 5 steps

ruby

class WeeklySignupsReport
  DEFAULT_WEEKS = 12
 
  def initialize(weeks: DEFAULT_WEEKS, source: User.all)

Building a weekly signups report in Rails

service object aggregation group by

Intermediate 7 steps

ruby

class ApplicationController < ActionController::Base
  EXPERIMENTS = {
    checkout_button_color: %w[control blue green],
    onboarding_flow: %w[control streamlined]

How A/B test cohorts are assigned in Rails

a-b-testing cookies hashing

Intermediate 8 steps

ruby

class SnippetHighlighter
  CONTEXT_RADIUS = 60
  MAX_TERMS = 8

Building search-result snippets in Ruby

regular-expressions text-processing search

Intermediate 9 steps

ruby

require "openssl"
require "base32"
 
class TOTP

How TOTP one-time codes work in Ruby

hmac authentication totp

Intermediate 7 steps

ruby

class Coupon < ApplicationRecord
  has_many :redemptions, dependent: :destroy
 
  validates :code, presence: true, uniqueness: { case_sensitive: false }

Safe coupon redemption in Rails

validation contexts pessimistic locking scopes

Advanced 10 steps

ruby

class AdminConstraint
  def self.matches?(request)
    new(request).matches?
  end

How routing constraints gate admin routes in Rails

routing authorization constraints

Intermediate 8 steps

ruby

require "openssl"
require "base64"
 
module SecureToken

Authenticated encryption with AES-GCM in Ruby

encryption aes-gcm authentication

Advanced 8 steps

ruby

require "erb"
 
class TemplateRenderer
  class MissingVariableError < StandardError; end

A safe ERB template renderer in Ruby

metaprogramming method_missing binding

Intermediate 10 steps

ruby

class ReverseGeocodeSignupJob < ApplicationJob
  queue_as :default
 
  retry_on Geocoder::OverQueryLimitError, wait: 5.minutes, attempts: 3

How Rails jobs handle reverse geocoding

background-jobs error-handling geocoding

Intermediate 7 steps

ruby

def wrap_text(text, width = 80)
  raise ArgumentError, "width must be positive" unless width.positive?
 
  text.split(/\n/, -1).map do |paragraph|

How greedy text wrapping works in Ruby

string-processing greedy-algorithm text-wrapping

Intermediate 7 steps

ruby

class SyncInventoryJob < ApplicationJob
  queue_as :integrations
 
  retry_on Faraday::TimeoutError,

Resilient background jobs with retry_on in Rails

background-jobs error-handling retries

Intermediate 8 steps

ruby

class Pluralizer
  IRREGULARS = {
    "person" => "people",
    "child" => "children",

Building an English pluralizer in Ruby

regular-expressions lookup-tables string-manipulation

Intermediate 8 steps

ruby

require 'set'
 
class CronSchedule
  FIELDS = %i[minute hour day month wday].freeze

Parsing and matching cron expressions in Ruby

parsing time-arithmetic sets

Intermediate 10 steps

ruby

module MarkdownHelper
  ALLOWED_TAGS = %w[
    p br strong em del a ul ol li blockquote code pre
    h1 h2 h3 h4 h5 h6 hr img table thead tbody tr th td

Safely rendering Markdown in a Rails helper

sanitization markdown security

Intermediate 8 steps

ruby

class ActivityFeed
  include Enumerable
 
  Entry = Struct.new(:record, :type, :occurred_at, keyword_init: true) do

Building a paginated activity feed in Rails

enumerable pagination composition

Intermediate 9 steps