Ask: How to create Singleton Object to used in Route Handler?

[izzddalfk]

Hello. I wonder how to create a singleton object at initial runtime for used in route handlers later, i.e a service object.
For example, to achieve what I mean on a simple web server using Express it would look as follows.

import express from "express";
import pg from "pg";
...
// create database pool
const pool = new pg.Pool();

// initialize service dependencies
const dbStorage = new DatabaseStorage({ dbPool: pool });
const secretManager = new SecretManager();

// initialize service
const service = new Service({ dbStorage, secretManager });

const app = express();

app.get("/products", (req, res) => {
  const products = service.listProducts();

  res.json({
    ok: true,
    data: products,
    ts: Math.ceil(Date.now() / 1000)
  });
});

app.post("/products", (req, res) => {
  service.storeProduct(req.body);
  res.json({
    ok: true,
    ts: Math.ceil(Date.now() / 1000)
  });
});

I can achieve this approach by initialize the object in package file, like so:

// server/service/index.ts

// these dependencies are object that already created. Not a class.
import databaseStorage from "~/server/deps/storage"
import secretManager from "~/server/deps/secret-manager"

export class Service {
  #dbStorage;
  #secretManager
  constructor({ dbStorage, secretManager }) {
    this.#dbStorage = dbStorage;
    this.#secretManager = secretManager;
  }

  listProducts() {}

  storeProduct() {}
}

const service = new Service({
  dbStorage: databaseStorage,
  secretManager
});

export default service;

But with this approach, it's not testable. Because when Service class imported in test file, it should also import all service dependencies, which initializes those dependencies as well. Whereas in the test those dependencies will be mocked.

How to achieve this with nitro?
Thanks.

[JCtapuk]

You meant

// <root>/server/plugins/service.ts
import { service } from 'path_service'

declare module 'h3' {
 interface H3Context {
  service: typeof service
 }
}

export default defineNitroPlugin((nitroApp) => {
  nitro.hooks.hook("request",  (event) => {
    event.context.service = service
  });
})

// <root>/server/api/test.ts
export default defineEventHandler((event) => {
 const service = event.context.service
 
 // all code use service
});