Ruby code explainers

ruby

require "csv"
 
def parse_transaction_row(line)
  fields = CSV.parse_line(line, headers: false, skip_blanks: true)

Parsing one CSV transaction row in Ruby

parsing type-coercion error-handling

Intermediate 6 steps

ruby

class NewCommentNotifier < ApplicationNotifier
  deliver_by :database
 
  deliver_by :email do |config|

Multi-channel notifications with Noticed in Rails

notifications delivery-methods fan-out

Intermediate 6 steps

ruby

class DocumentsController < ApplicationController
  before_action :authenticate_user!
  before_action :set_document

Serving secure file downloads in Rails

authorization signed-urls active-storage

Intermediate 8 steps

ruby

require "bigdecimal"
 
module Money
  CENTS = BigDecimal("0.01")

Handling money safely with BigDecimal in Ruby

bigdecimal rounding currency

Intermediate 7 steps

ruby

class ApplicationJob < ActiveJob::Base
  retry_on ActiveRecord::Deadlocked, wait: 5.seconds, attempts: 3
  discard_on ActiveJob::DeserializationError

Instrumenting every job in Rails

active-job structured-logging retries

Intermediate 6 steps

ruby

class PasswordResetsController < ApplicationController
  RESET_PURPOSE = :password_reset
  RESET_EXPIRY = 15.minutes

Password resets with signed global IDs in Rails

authentication signed-tokens global-id

Intermediate 9 steps

ruby

require "yaml"
require "pathname"
 
class AppConfig

A typed config loader in Ruby

yaml configuration recursion

Intermediate 8 steps

ruby

module ProductsHelper
  def cached_product_row(product)
    cache [product, current_user.role] do
      render partial: "products/row", locals: { product: product }

Russian doll caching that busts itself in Rails

fragment-caching cache-invalidation associations

Intermediate 4 steps

ruby

def build_pivot_table(sales)
  pivot = sales.each_with_object(Hash.new { |h, k| h[k] = Hash.new(0.0) }) do |record, table|
    region = record.fetch(:region)
    quarter = record.fetch(:quarter)

Building a pivot table in Ruby

aggregation nested-hashes default-values

Intermediate 9 steps

ruby

class DigestMailer < ApplicationMailer
  default from: "notifications@example.com"
 
  def weekly_digest(user)

Building a weekly digest email in Rails

mailers active-record query-scopes

Intermediate 6 steps

ruby

class OrdersController < ApplicationController
  rescue_from ActiveRecord::RecordNotUnique, with: :handle_duplicate_submission
 
  def create

Idempotent order creation in Rails

idempotency database-constraints error-handling

Intermediate 8 steps

ruby

class InventoryItem < ApplicationRecord
  belongs_to :warehouse
 
  validates :quantity, numericality: { greater_than_or_equal_to: 0 }

Safe inventory updates in Rails

concurrency pessimistic-locking optimistic-locking

Advanced 7 steps

ruby

require "forwardable"
 
class ShoppingCart
  extend Forwardable

Delegation in Ruby with Forwardable

delegation composition enumerable

Intermediate 9 steps

ruby

class PaymentMethod < ApplicationRecord
  belongs_to :account
 
  encrypts :card_number, deterministic: false

How Rails encrypts sensitive payment fields

encryption validation scopes

Intermediate 9 steps

ruby

require "zlib"
require "stringio"
require "base64"

Compress-and-encode payloads in Ruby

compression encoding io-streams

Intermediate 8 steps

ruby

class SignupValidator
  EMAIL_REGEX = /\A[^@\s]+@[^@\s]+\.[^@\s]+\z/
  MIN_PASSWORD_LENGTH = 8

Building a plain-Ruby signup validator

validation regex default-hash

Intermediate 7 steps

ruby

class QueryBuilder
  def initialize(table)
    @table = table
    @wheres = []

How a chainable SQL query builder works

fluent-interface method-chaining builder-pattern

Intermediate 8 steps

ruby

class DurationParser
  UNIT_SECONDS = {
    'w' => 604_800,
    'd' => 86_400,

Parsing duration strings into seconds in Ruby

parsing regular-expressions validation

Intermediate 7 steps