koa-depsi

Koa-depsi

This package allow you to easily inject dependencies in your koa app. In the example below we inject a database connection. This allow us to call the database from our handlers by using the ctx.deps.db object.

Of course injecting dependencies is usefull in testing context. This middleware will allow you to inject a fake db client through your Koa application to avoid calling a real database in your routes.

/app.js

const Koa = require('koa')
const koadepsi = require('koa-depsi')

function createApp(dependencies = {}) {
  const app = new Koa()

  /**
   * This will expose the object dependencies on the koa context : ctx.deps
   */
  app.use(koadepsi(dependencies))

  /**
   * If you use koa-router you can inject dependencies on specific routes only
   */
  const Router = require('koa-router');
  const router = new Router();
  router.use('/products', koadepsi(dependencies.productsController))

  return app
}

module.exports = createApp

/index.js

const database = require('whatever-db-you-want')
const app = require('./app')

const dependencies = { db: database }

app(dependencies).listen()

/routes/users/getById.js

async function getUserById(ctx) {
  /**
   * Here you can retrieve your database connection from the Koa context
   */
  const db = ctx.deps.db
  const user = await db.user.getById(ctx.params.id)
  ctx.status = 200
  ctx.body = { user }
}

module.exports = getUserById