Code Explainers

Browse the library

java 
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

Building a trie for autocomplete in Java

trie prefix-tree recursion
Intermediate 8 steps
go 
package handlers
 
import (
	"net/http"

Serving embedded static meta files in Gin

embedding static assets http caching
Intermediate 6 steps
php 
<?php
 
namespace App\Providers;
 

Subdomain multi-tenancy routing in Laravel

multi-tenancy service-container route-binding
Advanced 7 steps
ruby 
class KeyTransformer
  def self.camelize(data)
    new.camelize(data)
  end

Recursively camelizing nested Ruby data

recursion data-transformation pattern-matching
Intermediate 7 steps
typescript 
import { Injectable, NestInterceptor, ExecutionContext, CallHandler } from '@nestjs/common';
import { Observable, catchError, concatMap, finalize } from 'rxjs';
import { DataSource, QueryRunner } from 'typeorm';
 

Wrapping requests in a transaction with NestJS

interceptors transactions rxjs
Advanced 7 steps
python 
from django import template
from django.urls import reverse, NoReverseMatch
from django.utils.html import format_html
 

Active nav-link template tags in Django

template tags url routing active state
Intermediate 7 steps
javascript 
import { useReducer, useEffect } from "react";
 
const initialState = { status: "idle", data: null, error: null };
 

Building a data-fetching hook in React

custom-hooks usereducer data-fetching
Intermediate 9 steps
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