Code Explainers
Browse the library
ruby
class ToastBroadcaster include ActionView::RecordIdentifier def self.broadcast_to(user, message:, type: :notice)
How Turbo Stream toasts broadcast in Rails
turbo-streams
service-object
real-time
Intermediate
6 steps
typescript
import { NestFactory } from '@nestjs/core'; import { DocumentBuilder, SwaggerModule } from '@nestjs/swagger'; import { ValidationPipe } from '@nestjs/common'; import { ApiProperty } from '@nestjs/swagger';
Wiring validation and Swagger docs in NestJS
validation
openapi
decorators
Intermediate
8 steps
python
from fastapi import APIRouter, BackgroundTasks, Depends, HTTPException, status from pydantic import BaseModel, EmailStr from sqlalchemy.orm import Session
Building a signup endpoint in FastAPI
dependency-injection
request-validation
background-tasks
Intermediate
8 steps
javascript
const ROLE_PERMISSIONS = { admin: ['users:read', 'users:write', 'billing:read', 'billing:write'], manager: ['users:read', 'billing:read'], member: ['users:read'],
Role-based permissions middleware in Express
authorization
middleware
rbac
Intermediate
9 steps
rust
use axum::{extract::{Path, State}, http::StatusCode, Json}; use dashmap::DashMap; use serde::Serialize; use std::sync::Arc;
Request coalescing in an Axum handler
caching
concurrency
request-coalescing
Advanced
8 steps
java
public interface GitHubClient { @GetExchange("/users/{username}") GitHubUser getUser(@PathVariable String username);
Declarative HTTP clients in Spring
http-client
declarative-api
proxy
Intermediate
8 steps
php
<?php namespace App\Console\Commands;
Releasing stale document locks in Laravel
artisan-command
transactions
row-locking
Intermediate
6 steps
ruby
class TemplateInterpolator PLACEHOLDER = /\{\{\s*([\w.]+)\s*\}\}/ def initialize(strict: false)
Interpolating templates with dotted keys in Ruby
regex
string-interpolation
hash-traversal
Intermediate
6 steps
typescript
import { Component, Input } from '@angular/core'; interface Order { id: string;
How Angular ICU plurals localize an order summary
i18n
pluralization
standalone-component
Intermediate
8 steps
python
from django import forms from django.utils import timezone from .models import Reservation
Multi-field validation in a Django ModelForm
form validation
cross-field validation
modelform
Intermediate
7 steps
javascript
function attachThousandSeparators(input, { locale = 'en-US' } = {}) { const formatter = new Intl.NumberFormat(locale); const groupSep = formatter.format(11111).replace(/\d/g, '')[0] || ','; const decimalSep = formatter.format(1.1).replace(/\d/g, '')[0] || '.';
Live thousand separators without losing the caret
dom
intl
caret-preservation
Advanced
8 steps
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