Code Explainers

Browse the library

ruby 
module Paginatable
  extend ActiveSupport::Concern
 
  private

A reusable pagination concern in Rails

pagination concerns http-headers
Intermediate 8 steps
php 
<?php
 
namespace App\Broadcasting;
 

Authorizing presence channels in Laravel

broadcasting authorization presence-channels
Intermediate 3 steps
go 
package config
 
import (
	"fmt"

A thread-safe config singleton in Go

singleton concurrency environment-variables
Intermediate 7 steps
python 
from functools import wraps
import asyncio
 
from fastapi import APIRouter, FastAPI, Request

Per-route request timeouts in FastAPI

decorators async timeouts
Intermediate 6 steps
rust 
use std::net::Ipv4Addr;
use std::str::FromStr;
 
#[derive(Debug, Clone, Copy)]

Parsing and matching IPv4 CIDR ranges in Rust

bitwise-operations parsing error-handling
Intermediate 8 steps
typescript 
type CsvColumn<T> = {
  header: string;
  value: (row: T) => string | number | boolean | null | undefined;
};

Building a type-safe CSV writer in TypeScript

generics serialization escaping
Intermediate 7 steps
javascript 
const express = require('express');
const app = express();
 
app.get('/health', (req, res) => res.json({ status: 'ok' }));

Graceful shutdown in an Express server

graceful-shutdown signal-handling connection-tracking
Advanced 9 steps
java 
@RestController
@RequestMapping("/api/products")
public class ProductSearchController {
 

Binding collection query params in Spring

rest-api query-parameters dependency-injection
Intermediate 6 steps
ruby 
class Api::MessagesController < ApiController
  before_action :authenticate_api_key!
 
  rate_limit to: 100,

Layered API rate limiting in Rails

rate-limiting api-authentication throttling
Intermediate 9 steps
php 
<?php
 
namespace App\Http\Middleware;
 

Resolving the current team in Laravel middleware

middleware multi-tenancy cookies
Intermediate 8 steps
go 
package scheduler
 
import (
	"container/heap"

A priority job queue with Go's container/heap

priority-queue heap interfaces
Intermediate 9 steps
python 
import os
from pathlib import Path
 
BASE_DIR = Path(__file__).resolve().parent.parent.parent

How a Django settings module is wired

configuration environment-variables middleware
Intermediate 8 steps
rust 
use std::sync::OnceLock;
 
static CRC_TABLE: OnceLock<[u32; 256]> = OnceLock::new();
 

Table-driven CRC32 with lazy init in Rust

checksums lazy-initialization lookup-tables
Intermediate 8 steps
typescript 
import { parsePhoneNumberFromString, CountryCode } from 'libphonenumber-js';
 
export interface NormalizedPhone {
  e164: string;

Normalizing phone numbers to E.164 in TypeScript

validation normalization error-handling
Intermediate 7 steps
java 
import java.util.ArrayDeque;
import java.util.Deque;
import java.util.Map;
 

Evaluating math expressions with two stacks

stacks parsing operator-precedence
Intermediate 9 steps
ruby 
class Order < ApplicationRecord
  include AASM
 
  belongs_to :warehouse

Modeling an order lifecycle with AASM in Rails

state machine guards callbacks
Intermediate 10 steps
php 
<?php
 
namespace App\Http\Controllers;
 

Broadcasting typing indicators in Laravel

websockets authorization presence-channels
Intermediate 9 steps
go 
func UploadChunk(c *gin.Context) {
	uploadID := c.Param("uploadID")
	if !validUploadID.MatchString(uploadID) {
		c.JSON(http.StatusBadRequest, gin.H{"error": "invalid upload id"})

Resumable chunked uploads in Gin

file-upload content-range streaming
Advanced 9 steps