Code Explainers

Browse the library

rust 
use std::sync::{Arc, Mutex, MutexGuard};
use std::time::Instant;
 
pub struct TimedGuard<'a, T> {

A self-timing mutex guard in Rust

raii mutex deref
Advanced 7 steps
ruby 
require "openssl"
require "base64"
 
module WebhookSignature

Signing and verifying webhooks in Ruby

hmac cryptography webhooks
Intermediate 7 steps
go 
package httpx
 
import (
	"net/http"

A retrying HTTP transport in Go

http middleware retry
Intermediate 8 steps
php 
<?php
 
namespace App\Notifications;
 

How a queued weekly digest email works in Laravel

notifications queues email
Intermediate 7 steps
javascript 
import { parsePhoneNumberFromString } from 'libphonenumber-js';
 
export class PhoneValidationError extends Error {
  constructor(message, code) {

Normalizing phone numbers with typed errors

validation error-handling custom-errors
Intermediate 6 steps
typescript 
import { Injectable, computed, inject, signal } from '@angular/core';
import { HttpClient } from '@angular/common/http';
import { firstValueFrom } from 'rxjs';
 

Optimistic updates with Angular signals

signals optimistic-updates state-management
Intermediate 9 steps
java 
@RestControllerAdvice
public class GlobalExceptionHandler {
 
    private static final Logger log = LoggerFactory.getLogger(GlobalExceptionHandler.class);

Centralized error handling in Spring

exception-handling problemdetail rest-api
Intermediate 7 steps
python 
import os
from datetime import datetime, timezone
 
import jwt

JWT bearer auth as a FastAPI dependency

authentication jwt dependency-injection
Intermediate 7 steps
rust 
use std::error::Error;
use std::path::Path;
 
use serde::Deserialize;

Custom CSV deserialization with serde in Rust

serde csv deserialization
Intermediate 7 steps
ruby 
class CartMergeService
  def initialize(guest_cart:, user_cart:)
    @guest_cart = guest_cart
    @user_cart = user_cart

Merging a guest cart into a user cart in Rails

service object transactions idempotency
Intermediate 7 steps
go 
package config
 
import (
	"fmt"

Loading typed config from environment variables in Go

configuration environment-variables type-parsing
Beginner 8 steps
php 
public function importCustomers(UploadedFile $file): array
{
    $errors = [];
    $imported = 0;

Validating a CSV import in Laravel

csv-parsing validation error-accumulation
Intermediate 8 steps
javascript 
const express = require('express');
const { z } = require('zod');
const router = express.Router();
 

Validating query params with Zod in Express

validation schema-parsing query-building
Intermediate 9 steps
typescript 
type EventMap = Record<string, unknown>;
 
type Handler<T> = (payload: T) => void;
 

A type-safe event bus in TypeScript

generics event-emitter type-safety
Advanced 7 steps
java 
public List<String> collectTagsFromArticles(List<Article> articles) {
    return articles.stream()
        .flatMap(article -> article.getTags().stream())
        .map(String::trim)

Flattening nested data with Java streams

streams flatmap collectors
Intermediate 7 steps
python 
import logging
import traceback
 
from flask import Blueprint, jsonify, request

Centralized JSON error handling in Flask

error-handling blueprints json-api
Intermediate 5 steps
rust 
use std::time::Duration;
 
use axum::{extract::State, http::StatusCode, response::IntoResponse, Json};
use serde::Serialize;

A timeout-guarded health check in Axum

health-check timeout error-handling
Intermediate 6 steps
ruby 
require 'monitor'
 
class TokenBucket
  include MonitorMixin

A thread-safe token bucket rate limiter in Ruby

rate-limiting concurrency thread-safety
Intermediate 8 steps