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Basic Setup ​

Problem ​

You need to wire together a small application graph — a logger and a service that depends on it — with typed tokens, lazy construction, and automatic cleanup.

Solution ​

Use token() to define each dependency contract, container.value() or container.factory() to register providers, and await container.resolve() to get an instance.

ts
import { createContainer, token } from '@vielzeug/conduit';

const Logger = token<{ log(message: string): void }>('Logger');
const Service = token<{ run(): Promise<void> }>('Service');

const container = createContainer();

container.value(Logger, {
  log(message) {
    console.log(message);
  },
});

container.factory(Service, async (r) => {
  const logger = await r.resolve(Logger);
  return {
    async run() {
      logger.log('running');
    },
  };
});

const service = await container.resolve(Service);
await service.run(); // logs "running"

await container.dispose();

Pitfalls ​

  • Calling container.resolve() before container.value() or container.factory() throws ProviderNotFoundError. Register all providers before resolving.
  • Passing a token of type Token<A> where Token<B> is expected is a type error at compile time. Each token() call creates a distinct symbol even when descriptions match.