Code Explainers

Code explainers tagged #callbacks

ruby 
class Order < ApplicationRecord
  include AASM
 
  belongs_to :warehouse

Modeling an order lifecycle with AASM in Rails

state machine guards callbacks
Intermediate 10 steps
ruby 
module Authenticatable
  extend ActiveSupport::Concern
 
  included do

JWT authentication as a Rails concern

authentication jwt concerns
Intermediate 6 steps
ruby 
class Contact < ApplicationRecord
  PHONE_FORMATS = {
    "US" => /\A\+1\d{10}\z/,
    "GB" => /\A\+44\d{10}\z/,

Country-aware phone validation in Rails

validation callbacks regex
Intermediate 6 steps
ruby 
class Product < ApplicationRecord
  belongs_to :category, touch: true
 
  has_many :reviews, dependent: :destroy

How Rails models wire up associations

active record associations validations
Intermediate 7 steps
java 
public List<OrderSummary> streamRecentOrders(LocalDateTime since, Consumer<OrderSummary> handler) {
    String sql = """
        SELECT id, customer_id, total_cents, status, created_at
        FROM orders

Streaming large JDBC result sets safely

jdbc streaming resource-management
Intermediate 7 steps
ruby 
class Order
  class InvalidTransition < StandardError; end
 
  TRANSITIONS = {

A state machine for order transitions in Ruby

state-machine data-driven error-handling
Intermediate 8 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 PaymentMethod < ApplicationRecord
  belongs_to :account
 
  encrypts :card_number, deterministic: false

How Rails encrypts sensitive payment fields

encryption validation scopes
Intermediate 9 steps
ruby 
class Account < ApplicationRecord
  has_many :projects, dependent: :destroy_async
  has_many :memberships, dependent: :destroy_async
  has_many :invoices, dependent: :restrict_with_error

Safely closing an Account in Rails

associations callbacks transactions
Intermediate 9 steps
python 
import os
import time
from pathlib import Path
 

Polling a directory for file changes in Python

polling filesystem set-operations
Intermediate 8 steps
ruby 
class Product < ApplicationRecord
  belongs_to :account
 
  after_save :record_audit_trail

Building an audit trail with Rails callbacks

callbacks audit-logging dirty-tracking
Intermediate 7 steps
javascript 
function createCountdownTimer(durationSeconds, { onTick, onComplete } = {}) {
  let remaining = durationSeconds;
  let intervalId = null;
 

Building a countdown timer with closures

closures factory-function timers
Intermediate 9 steps
php 
<?php
 
namespace App\Events;
 

A priority event dispatcher in PHP

observer-pattern callbacks priority-ordering
Intermediate 8 steps
ruby 
class Comment < ApplicationRecord
  belongs_to :post
  belongs_to :author, class_name: "User"
 

Live-updating comments with Turbo in Rails

turbo-streams callbacks associations
Intermediate 8 steps
ruby 
class Comment < ApplicationRecord
  belongs_to :commentable, polymorphic: true, counter_cache: true
  belongs_to :author, class_name: "User"
 

How polymorphic comments work in Rails

polymorphic-association concerns counter-cache
Intermediate 8 steps
ruby 
module SoftDeletable
  extend ActiveSupport::Concern
 
  included do

How a soft-delete concern works in Rails

concerns soft-delete scopes
Intermediate 8 steps
ruby 
class Post < ApplicationRecord
  before_validation :generate_slug, on: :create
 
  validates :slug, presence: true, uniqueness: true

How a Rails model builds unique slugs

slugs callbacks validations
Intermediate 7 steps
ruby 
class EventEmitter
  def initialize
    @listeners = Hash.new { |hash, key| hash[key] = [] }
  end

Building an EventEmitter in Ruby

pub-sub closures callbacks
Intermediate 7 steps