ts-registry-express

Custom ts-registry scope provider for Express requests.

Quick Start

import * as express from 'express';
import { Registry } from 'ts-registry';
import { middleware, request } from 'ts-registry-express';

// define a request-scoped service
const registry = new Registry();
registry
  .for('my-service')
  .withScope(request)
  .use(() => new MyService())

// use the middleware
const app = express();
app.use(middleware);

// get an instance of the service
app.get('/', (req, res) => {
  // service instance is unique to this request
  const service = registry.getService('my-service');
})

Access to the current Request

The target scope for this ScopeProvider is the current Request object and can be accessed via the second parameter of the service initializer.

Example:

registry
  .for('my-service')
  .withScope(request)
  .use((_get, req) => new MyService(req.session))

Because service instantiation is deferred, request-scoped service initializers can be defined outside of standard Express middleware, routers, or other handlers. However, when the registry.get() is called during a request (even if the call is made from another function or module) the service initializer is passed the instance of the current request as the second argument.

Note that if you hold onto a reference of req within either the service intializer or other code, it will not be garbage collected and will lead to a memory leak.

Troubleshooting

If you encounter the error "Request not found in context", it means the middleware hasn't been properly registered. Make sure to:

Import and use the ts-registry-express middleware
Register them before any routes that need the context

import express from 'express';
import { middleware } from 'ts-registry-express';

const app = express();

// Register middleware first
app.use(middleware);

// Then register your routes that get request-scoped services
app.get('/', (req, res) => {
  const service = registry.getService('my-service');
});

If you're using multiple routers, remember to register the middleware on each router that needs the context.

If you're still experiencing issues, please check:

The order of middleware registration
That you're using the latest version of the package
Your Node.js version compatibility
That all required dependencies are properly installed