Koa

Quick guide to integrate Vla with Koa.

View Example App

Install

npm install vla

Create Kernel

Create src/data/kernel.ts:

import { Kernel } from 'vla'

export const kernel = new Kernel()

Set Up Middleware

Add Vla middleware to your Koa app:

import Koa from 'koa'
import Router from '@koa/router'
import { Vla } from 'vla'
import { kernel } from './data/kernel'

const app = new Koa()
const router = new Router()

// Add Vla middleware
app.use(async (ctx, next) => {
  await Vla.withKernel(kernel.scoped(), next)
})

// Your routes...
router.get('/users/:id', async (ctx) => {
  const user = await GetUser.invoke(ctx.params.id)
  ctx.body = user
})

app.use(router.routes())
app.listen(3000)

This creates a scoped kernel for each request.

Use in Routes

src/data/users.actions.ts

import { Vla } from 'vla'

class GetUser extends Vla.Action {
  async handle(id: string) {
    // Your logic here
    return { id, name: 'User' }
  }
}

// src/server.ts
router.get('/users/:id', async (ctx) => {
  const user = await GetUser.invoke(ctx.params.id)
  ctx.body = user
})

Access Koa Context (Optional)

To access the Koa context object, create a context:

src/data/context.ts

import { Vla } from 'vla'
import type { Context } from 'koa'

export const AppContext = Vla.createContext<{
  ctx: Context
}>()

Update your middleware:

import { Vla } from 'vla'
import { kernel } from './data/kernel'
import { AppContext } from './data/context'

app.use(async (ctx, next) => {
  await Vla.withKernel(
    kernel.scoped().context(AppContext, { ctx }),
    next
  )
})

Use in your classes:

class GetCurrentUser extends Vla.Action {
  ctx = this.inject(AppContext)

  async handle() {
    const sessionId = this.ctx.ctx.cookies.get('session_id')
    // Use context data
  }
}

That’s It

You’re ready to use Vla in your Koa app. Check out the guides to learn how to structure your code with Actions, Services, and Repos.