Express

Quick guide to integrate Vla with Express.

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 Express app:

import express from 'express'
import { Vla } from 'vla'
import { kernel } from './data/kernel'

const app = express()

// Add Vla middleware
app.use((req, res, next) => {
  Vla.withKernel(kernel.scoped(), next)
})

// Your routes...
app.get('/users/:id', async (req, res) => {
  const user = await GetUser.invoke(req.params.id)
  res.json(user)
})

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
app.get('/users/:id', async (req, res) => {
  const user = await GetUser.invoke(req.params.id)
  res.json(user)
})

Access Request/Response (Optional)

To access the Express request and response objects, create a context:

src/data/context.ts

import { Vla } from 'vla'
import type { Request, Response } from 'express'

export const AppContext = Vla.createContext<{
  req: Request
  res: Response
}>()

Update your middleware:

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

app.use((req, res, next) => {
  Vla.withKernel(
    kernel.scoped().context(AppContext, { req, res }),
    next
  )
})

Use in your classes:

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

  async handle() {
    const sessionId = this.ctx.req.cookies.session_id
    // Use request data
  }
}

That’s It

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