Code Explainers

Code explainers tagged #dependency-injection

typescript 
import { Module } from '@nestjs/common';
import { TypeOrmModule } from '@nestjs/typeorm';
import { BullModule } from '@nestjs/bullmq';
 

How a NestJS feature module wires up

dependency-injection modularity orm
Intermediate 7 steps
typescript 
import {
  Controller,
  Get,
  Query,

Validating paginated queries in NestJS

pagination validation pipes
Intermediate 7 steps
python 
import pytest
from fastapi.testclient import TestClient
from sqlalchemy import create_engine
from sqlalchemy.orm import sessionmaker

Testing FastAPI routes with dependency overrides

testing fixtures dependency-injection
Intermediate 7 steps
typescript 
import {
  Controller,
  Post,
  UploadedFile,

Handling avatar uploads in NestJS

file-upload validation interceptors
Intermediate 7 steps
java 
@RestController
@RequestMapping("/api/reports")
public class OrderReportController {
 

Streaming a CSV export in Spring

streaming csv-export backpressure
Intermediate 9 steps
typescript 
import { Injectable, UnauthorizedException } from '@nestjs/common';
import { PassportStrategy } from '@nestjs/passport';
import { ExtractJwt, Strategy } from 'passport-jwt';
import { ConfigService } from '@nestjs/config';

How a JWT strategy authenticates in NestJS

authentication jwt passport
Intermediate 7 steps
python 
import os
from datetime import timedelta
 
 

Class-based config in a Flask app factory

configuration app-factory inheritance
Intermediate 7 steps
typescript 
import { Injectable, Logger, OnApplicationShutdown } from '@nestjs/common';
import { InjectRedis } from '@nestjs-modules/ioredis';
import Redis from 'ioredis';
import { DataSource } from 'typeorm';

Graceful shutdown hooks in NestJS

graceful-shutdown lifecycle-hooks dependency-injection
Intermediate 7 steps
typescript 
import { Injectable, OnModuleInit, Logger } from '@nestjs/common';
import { ConfigService } from '@nestjs/config';
import { Cron, CronExpression } from '@nestjs/schedule';
 

A self-refreshing feature flags provider in NestJS

caching scheduled-tasks dependency-injection
Intermediate 8 steps
java 
@Controller
public class BookController {
 
    private final BookService bookService;

Solving GraphQL N+1 with batch mapping in Spring

graphql n+1-problem batching
Intermediate 8 steps
php 
<?php
 
namespace App\View\Composers;
 

How a Laravel view composer feeds the navigation

view-composer caching dependency-injection
Intermediate 5 steps
java 
@Component
required to import
public class OutboxEventPublisher {
 

The transactional outbox pattern in Spring

transactional-outbox event-driven reliability
Advanced 7 steps
typescript 
import { Injectable } from '@angular/core';
import { CanDeactivateFn } from '@angular/router';
import { inject } from '@angular/core';
import { MatDialog } from '@angular/material/dialog';

Guarding navigation with CanDeactivate in Angular

route-guards functional-guards dependency-injection
Intermediate 7 steps
java 
package com.example.payments.config;
 
import org.springframework.beans.factory.annotation.Value;
import org.springframework.context.annotation.Bean;

Configuring a Stripe RestClient in Spring

dependency-injection http-client configuration
Intermediate 7 steps
typescript 
import { Controller, Get, Param, Post, Body, Version, VERSION_NEUTRAL } from '@nestjs/common';
import { UsersService } from './users.service';
import { CreateUserDto } from './dto/create-user.dto';
 

How API versioning works in NestJS

api-versioning routing dependency-injection
Intermediate 9 steps
java 
@RefreshScope
@Component
public class FeatureSettings {
 

Refreshable feature settings in Spring

caching configuration dependency-injection
Intermediate 7 steps
typescript 
import { Injectable, NotFoundException } from '@nestjs/common';
import { EventEmitter2, OnEvent } from '@nestjs/event-emitter';
import { InjectRepository } from '@nestjs/typeorm';
import { Repository } from 'typeorm';

Decoupling side effects with NestJS events

event-driven decoupling dependency-injection
Intermediate 7 steps
php 
<?php
 
namespace App\Jobs;
 

Building a unique queued job in Laravel

queues background-jobs idempotency
Intermediate 7 steps