Code Explainers

Browse the library

ruby 
require "timeout"
require "net/http"
 
class RemoteInventoryClient

Bounding a slow HTTP call with Timeout in Ruby

timeout error-handling http
Intermediate 6 steps
rust 
use axum::{
    body::Body,
    extract::Path,
    http::{header, HeaderMap, HeaderValue, StatusCode},

HTTP range requests for video streaming in Axum

http-range-requests streaming async-io
Advanced 8 steps
java 
@Entity
@Table(name = "orders")
@SQLDelete(sql = "UPDATE orders SET deleted = true, deleted_at = now() WHERE id = ?")
@Where(clause = "deleted = false")

Soft deletes with Hibernate in Spring

soft-delete jpa hibernate
Intermediate 9 steps
javascript 
import { useState, useEffect, useCallback } from 'react';
 
function getColumnCount(width) {
  if (width < 640) return 1;

A responsive column hook in React

custom-hooks debouncing responsive-design
Intermediate 7 steps
php 
<?php
 
namespace App\Services\Reports;
 

Streaming a monthly revenue CSV in Laravel

csv-export lazy-collections eloquent-query
Intermediate 8 steps
python 
def is_valid_card_number(number: str) -> bool:
    digits = [int(c) for c in number if c.isdigit()]
 
    if len(digits) < 13 or len(digits) > 19:

Validating card numbers with the Luhn check

checksum validation luhn-algorithm
Intermediate 6 steps
go 
func (h *ArticleHandler) Create(c *gin.Context) {
	var req struct {
		Title   string `json:"title" binding:"required"`
		Body    string `json:"body" binding:"required"`

Handling a POST request in Gin

request binding validation http status codes
Intermediate 7 steps
typescript 
import {
  CanActivate,
  ExecutionContext,
  Injectable,

Role-based access with a NestJS guard

authorization guards decorators
Intermediate 6 steps
ruby 
require "base64"
require "json"
 
module Attachment

Packing binary attachments into JSON

serialization base64 json
Intermediate 8 steps
rust 
use std::sync::mpsc;
use std::thread;
use std::time::Duration;
 

Running work with a timeout in Rust

concurrency channels timeout
Intermediate 7 steps
java 
@GetMapping("/files/{id}")
public ResponseEntity<StreamingResponseBody> download(
        @PathVariable String id,
        @RequestHeader(value = HttpHeaders.RANGE, required = false) String rangeHeader) throws IOException {

HTTP range requests in Spring

http-range streaming file-io
Advanced 10 steps
javascript 
function initCharacterCounter(textarea, options = {}) {
  const maxLength = options.maxLength ?? 280;
  const warnThreshold = options.warnThreshold ?? 0.9;
 

A live character counter for textareas

dom closures accessibility
Intermediate 7 steps
php 
<?php
 
namespace App\Services;
 

Computing rolling averages in Laravel

rolling-average date-ranges collections
Intermediate 8 steps
python 
from django.db.models import Q
 
from .models import Order
 

DISTINCT ON queries in Django

orm querysets postgresql
Intermediate 7 steps
go 
package cache
 
import (
	"sync"

A thread-safe TTL cache in Go

concurrency mutex caching
Intermediate 9 steps
typescript 
import { Injectable, computed, effect, signal } from '@angular/core';
 
export interface CartLine {
  id: string;

A signal-based cart store in Angular

signals reactivity computed-state
Intermediate 8 steps
ruby 
require "yaml"
 
class FrontMatter
  DELIMITER = /\A---\s*\n(.*?)\n---\s*\n?(.*)\z/m

Parsing YAML front matter in Ruby

parsing regular-expressions yaml
Intermediate 8 steps
rust 
use axum::{extract::State, response::IntoResponse, Json};
use serde::{Deserialize, Serialize};
use serde_json::{json, Value};
use std::sync::Arc;

Building a JSON-RPC 2.0 handler in Axum

json-rpc serde request-dispatch
Intermediate 8 steps