jeffijoe

describe('Todos Service', function () {
  beforeEach(() {
    subject = makeTodosService({
      db: testDatabaseSomehow
    })
  })
  
  it('works', async function () {
    const todos = await subject.getTodos()
    expect(todos.length).to.equal(3)

jeffijoe

import assert from 'assert'

// Using object destructuring to make it look good.
export function makeTodosService({
  // "repository" is a fancy term to descibe an object
  // that is used to retrieve data from a datasource - the actual
  // data source does not matter. Could be a database, a REST API,
  // or some IoT things like sensors or whatever.
  todosRepository,
  // We also want info about the user that is using the service,

jeffijoe

// Let's do an in-memory implementation for now.
const _todos = []

export default class TodosRepository {
  // Marking all methods async makes them return promises!
  async find(query) {
    const filtered = _todos.filter((todo) => {
      // Check the user ID
      if (todo.userId !== query.userId) 
        return false

jeffijoe

import makeTodosService from './todosService'
import TodosRepository from './todosRepository'

describe('Todos System', function () {
  it('works', async function () {
    // This is how DI is done manually
    const todosService = makeTodosService({
      todosRepository: new TodosRepository(),
      // Let's fake it til we make it!
      currentUser: {

jeffijoe

const currentUser = {
  id: 123,
  name: 'Jeff'
}

const todosRepository = new TodosRepository()

const todosService = makeTodosService({
  todosRepository,
  currentUser

jeffijoe

const router = new KoaRouter()

router.get('/todos', async (ctx) => {
  const todosService = makeTodosService({
    todosRepository: new TodosRepository(),    
    // Our Koa request knows about the current user 
    currentUser: ctx.state.user 
  })
  
  ctx.body = await todosService.getTodos(ctx.request.query)

jeffijoe

import { createContainer, asClass, asFunction } from 'awilix'
import makeTodosService from './todosService'
import TodosRepository from './todosRepository'

export default function configureContainer () {
  const container = createContainer()
  
  // Ordering does not matter.
  container.register({
    // Notice the scoped() at the end - this signals

jeffijoe

import Koa from 'koa'
import KoaRouter from 'koa-router'
import { asValue } from 'awilix'
import { scopePerRequest, makeInvoker } from 'awilix-koa'
import configureContainer from './configureContainer'

const app = new Koa()
const router = new KoaRouter()
const container = configureContainer()

jeffijoe

// middleware/auth.js
export default async function authenticate (ctx, next) {
  // Do your auth stuff here.
  const decoded = extractTokenSomehow(ctx)
  const teamId = decoded.teamId
  const userId = decoded.userId

  // Use the User Repository and Team Repository (or a cache?) to fetch
  // our entities.
  // Resolve instances of these using Awilix's cradle proxy.

jeffijoe

import Koa from 'koa'
import parse from './busboy'
import AWS from 'aws-sdk'

const app = new Koa()

const s3 = new AWS.S3({ 
  params: { Bucket: 'myBucket' } 
})