codesnips
python 
import asyncio
from collections import defaultdict

from fastapi import WebSocket

FastAPI WebSocket Connection Manager for Broadcasting to Room Subscribers

fastapi websockets asyncio
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typescript 
import { SetMetadata } from '@nestjs/common';

export enum Role {
  User = 'user',
  Editor = 'editor',
  Admin = 'admin',

Role-Based Access Control in NestJS with a Custom Guard and @Roles Decorator

nestjs authorization rbac
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rust 
use std::cmp::{Ordering, Reverse};

#[derive(Debug, Clone)]
pub struct ScheduledTask<T> {
    pub priority: u8,
    pub seq: u64,

Priority Task Scheduler in Rust with BinaryHeap and Reverse Ordering

rust binary-heap scheduler
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rust 
use std::collections::HashMap;
use std::sync::{Arc, Mutex, PoisonError};

#[derive(Default)]
struct Metrics {
    per_endpoint: HashMap<String, u64>,

Thread-Safe Request Metrics with Arc, Mutex, and a Poison-Recovery Guard

rust concurrency arc
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ruby 
class Cart < ApplicationRecord
  has_many :cart_items, dependent: :destroy

  EXPIRY_WINDOW = 2.hours

  scope :active, -> { where(state: :active) }

Expire Stale Shopping Carts With a Rails Scope and a Recurring Reaper Job

rails activerecord background-jobs
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java 
package com.example.notifications;

import org.springframework.stereotype.Component;
import org.springframework.web.servlet.mvc.method.annotation.SseEmitter;

import java.io.IOException;

Live Browser Notifications with Spring Boot SseEmitter and a Broadcaster Service

spring-boot sse server-sent-events
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ruby 
Rails.application.routes.draw do
  resources :articles do
    resources :comments, shallow: true, only: %i[index new create show edit update destroy]
  end

  root "articles#index"

Nested Comments on Articles with Shallow Routing and Scoped Lookups in Rails

rails routing controllers
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python 
import base64
import json

from django.core.exceptions import BadRequest

Cursor-Paginated JSON Feed with a Django Class-Based ListView

django pagination cursor-pagination
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ruby 
class Order < ApplicationRecord
  has_many :line_items, inverse_of: :order, dependent: :destroy

  accepts_nested_attributes_for :line_items,
    allow_destroy: true,
    reject_if: ->(attrs) { attrs["product_id"].blank? && attrs["quantity"].blank? }

Validate Nested Attributes for an Order and Its Line Items in Rails

rails activerecord validations
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typescript 
import { z } from "zod";

export const signupSchema = z
  .object({
    email: z.string().min(1, "Email is required").email("Enter a valid email"),
    username: z

React Signup Form Validation With Zod and Field-Level Errors

react zod forms
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python 
import io
import os
from uuid import uuid4
from PIL import Image, UnidentifiedImageError

ALLOWED_FORMATS = {"JPEG", "PNG", "WEBP"}

Validate and Generate Image Thumbnails on a Flask Upload Endpoint With Pillow

flask pillow image-processing
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go 
package export

import (
	"encoding/csv"
	"log"
	"net/http"

Streaming Large CSV Exports in Go Without Buffering the Whole File

go http csv
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