Code Explainers

Code explainers tagged #dependency-injection

python 
from fastapi import APIRouter, Depends, HTTPException, status
 
from app.config import settings
from app.dependencies import get_current_user

Gating a FastAPI route behind a feature flag

feature-flags dependency-injection authorization
Intermediate 7 steps
python 
import csv
import io
from typing import Annotated
 

Content negotiation in FastAPI

content-negotiation dependency-injection http-headers
Intermediate 5 steps
typescript 
import { Routes } from '@angular/router';
import { inject } from '@angular/core';
import { HttpClient } from '@angular/common/http';
import { REPORT_API_URL } from './reports/report.tokens';

Route-scoped providers and lazy loading in Angular

routing dependency-injection lazy-loading
Intermediate 8 steps
typescript 
import { Component, inject } from '@angular/core';
import { combineLatest, map, startWith } from 'rxjs';
import { UserStore } from './user.store';
import { CartStore } from './cart.store';

The view model pattern in Angular

rxjs view-model reactive-streams
Intermediate 6 steps
python 
from fastapi import APIRouter, status
from fastapi.responses import JSONResponse
from sqlalchemy import text
from sqlalchemy.exc import SQLAlchemyError

Liveness vs readiness health checks in FastAPI

health-checks dependency-injection async
Intermediate 6 steps
typescript 
import { Injectable, UnauthorizedException } from '@nestjs/common';
import { PassportStrategy } from '@nestjs/passport';
import { Strategy } from 'passport-headerapikey';
import { ConfigService } from '@nestjs/config';

Building an API-key auth strategy in NestJS

authentication passport dependency-injection
Intermediate 8 steps
python 
from typing import Optional
 
from fastapi import APIRouter, Depends, HTTPException, status
from pydantic import BaseModel, EmailStr, Field

How PATCH partial updates work in FastAPI

partial-update validation dependency-injection
Intermediate 8 steps
python 
from fastapi import APIRouter, Depends, HTTPException, status
from pydantic import BaseModel
 
from .dependencies import get_current_user, get_project_service

Building a CRUD router with FastAPI

dependency-injection rest-api authentication
Intermediate 6 steps
typescript 
import { Component, inject } from '@angular/core';
import { FormBuilder, ReactiveFormsModule, Validators } from '@angular/forms';
import { HttpClient, HttpErrorResponse } from '@angular/common/http';
import { finalize } from 'rxjs';

A reactive signup form in Angular

reactive-forms validation dependency-injection
Intermediate 10 steps
rust 
use std::sync::Arc;
 
use axum::{
    extract::{FromRef, State},

Substate extraction with FromRef in Axum

state-management routing middleware
Intermediate 8 steps
typescript 
import { InjectionToken, inject, Provider, isDevMode } from '@angular/core';
import { WINDOW } from './window.token';
 
export interface AnalyticsConfig {

Layered config with an Angular InjectionToken

dependency-injection configuration factory-provider
Intermediate 8 steps
java 
@RestController
@RequestMapping("/api/products")
@Validated
public class ProductSearchController {

Validating query params in a Spring controller

validation pagination rest-api
Intermediate 8 steps
python 
import secrets
 
from fastapi import Depends, FastAPI, HTTPException, Security, status
from fastapi.security import APIKeyHeader

API key authentication as a FastAPI dependency

authentication dependency-injection api-keys
Intermediate 8 steps
java 
@Component
public class HeaderMergeFilter {
 
    private static final String PER_REQUEST_HEADERS = HeaderMergeFilter.class.getName() + ".headers";

Merging default and per-request headers in Spring

webclient filters http-headers
Intermediate 8 steps
typescript 
import { Injectable, inject } from '@angular/core';
import { HttpClient } from '@angular/common/http';
import { Observable, timer, throwError } from 'rxjs';
import { switchMap, takeWhile, filter, take, catchError } from 'rxjs/operators';

Polling a job until it finishes in Angular

rxjs polling observables
Intermediate 7 steps
php 
<?php
 
namespace App\Http\Controllers;
 

Handling Stripe webhooks in Laravel

webhooks signature-verification dependency-injection
Intermediate 7 steps
typescript 
import { Injectable, signal, computed, effect, inject } from '@angular/core';
import { DOCUMENT } from '@angular/common';
 
export type Theme = 'light' | 'dark';

A signal-based theme service in Angular

signals reactivity dependency-injection
Intermediate 7 steps
java 
@Component
public class RegionCacheWarmer implements SmartInitializingSingleton {
 
    private static final Logger log = LoggerFactory.getLogger(RegionCacheWarmer.class);

Warming a Spring cache at startup

caching startup-hook dependency-injection
Intermediate 7 steps