Code Explainers

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php 
<?php
 
namespace App\Models;
 

Auto-generating unique slugs in Laravel

eloquent model-events slugs
Intermediate 8 steps
python 
from datetime import datetime, timezone
 
from flask import abort
from sqlalchemy import Column, DateTime

Soft deletes with a custom SQLAlchemy Query in Flask

soft-delete mixin query-subclass
Advanced 7 steps
typescript 
type CompactOptions = {
  locale?: string;
  maximumFractionDigits?: number;
};

Caching Intl.NumberFormat for compact numbers

memoization internationalization caching
Intermediate 7 steps
rust 
use rand::Rng;
 
#[derive(Debug)]
pub struct WeightedChoice<T> {

Weighted random sampling in Rust

weighted-sampling generics binary-search
Intermediate 7 steps
javascript 
export default function DashboardLayout({ children, analytics, notifications }) {
  return (
    <div className="flex h-screen overflow-hidden">
      <Sidebar />

Parallel routes in a Next.js layout

parallel-routes layouts app-router
Intermediate 8 steps
go 
package middleware
 
import (
	"crypto/subtle"

Timing-safe API key auth in Gin

middleware authentication constant-time-compare
Intermediate 8 steps
ruby 
require "nokogiri"
require "open-uri"
require "set"
 

Extracting and normalizing links in Ruby

web-scraping url-parsing html-parsing
Intermediate 8 steps
java 
@Component
public class ApiKeyRotationFilter extends OncePerRequestFilter {
 
    private static final String API_KEY_HEADER = "X-Api-Key";

Building an API key rotation filter in Spring

servlet-filter authentication caching
Intermediate 10 steps
go 
package handlers
 
import (
	"context"

A custom Gin validator backed by Redis

validation redis struct-tags
Intermediate 8 steps
python 
class TrieNode:
    __slots__ = ("children", "is_word")
 
    def __init__(self):

Building a prefix trie in Python

trie tree-traversal recursion
Intermediate 7 steps
javascript 
function flatten(obj, prefix = '', result = {}) {
  for (const [key, value] of Object.entries(obj)) {
    const path = prefix ? `${prefix}.${key}` : key;
 

Flattening nested objects into dotted paths

recursion object-traversal accumulator
Intermediate 6 steps
typescript 
import {
  CallHandler,
  ExecutionContext,
  Injectable,

Deduping in-flight requests in NestJS

interceptor request-deduplication rxjs
Advanced 6 steps
php 
namespace App\Console\Commands;
 
use App\Models\Region;
use App\Services\ReportBuilder;

How a Laravel command warms report caches

caching cache-warming artisan-command
Intermediate 5 steps
ruby 
require "yaml"
require "date"
 
class Money

Custom YAML serialization in Ruby

serialization yaml custom-encoding
Intermediate 7 steps
java 
@Configuration
@EnableJpaAuditing(auditorAwareRef = "auditorAware")
public class AuditingConfig {
 

Automatic audit trails with Spring Data JPA

jpa-auditing security-context entity-listeners
Intermediate 7 steps
rust 
use std::collections::BTreeSet;
 
#[derive(Debug)]
pub enum FieldError {

Parsing a cron field in Rust

parsing error-handling enums
Intermediate 7 steps
go 
package trie
 
import "sort"
 

Building a frequency-ranked autocomplete trie in Go

trie autocomplete recursion
Intermediate 9 steps
python 
from flask import Blueprint, request, jsonify, abort
from sqlalchemy import update
 
from .models import db, Document

Optimistic locking in a Flask PATCH endpoint

optimistic-locking concurrency rest-api
Intermediate 7 steps