Wiry

Wiry is an unopinionated dependency injection container for your node or typescript appllication.

Design Goals

Your code should not be aware of Wiry.

You should have one file, or one layer that deals with configuring the container, but every other class or function should have no knowledge of a container. Classes will not have magic annotations that get processed, or assumptions of how the class will be used.

Features

• Automatic, async dependency resolution
• Get array of services by pattern (ie server.controllers.* as controllers: Controller[])
• Middleware/behaviours to wrap services (ie cache, etc.)

Usage

At its core, wiry allows you to register and retrieve services, while resolving their dependency trees for you. Services are defined within functions, so they can be fetched lazily and asynchronously. They can be functions, class instances, or any values that can be returned.

If the service has dependencies, pass it as the 3rd argument with an array of names, and they will be fed into the function for that service. Services can be defined in any order; they will be resolved when requested rather than when defined.

// class instance, depends on 'db' and 'cache'
container.registerService(
  'user-management',
  (db: Database, cache: Cache) => new UserManagement(db, cache),
  ['db', 'cache']
);

// register config
container.registerService('config', () => config);

// register database which depends on config
container.registerService(
  'db',
  (config: Config) => new Database(config.DB_CONNECTION_STRING),
  ['config']
);

// services can be returned with promises as well if they don't lazily connect for you
container.registerService(
  'cache',
  (config: Config) => {
    const redis = new Redis(config.CACHE_REDIS_HOST, config.CACHE_REDIS_PORT);
    return redis.connect(connection => {
      return new Cache(new RedisCacheBackend(redis));
    });
  },
  ['config']
);

// use the service
return container.get('user-management').then(service => {
  return service.createUser(/* ... */);
});

This keeps all of the wiring or dependency resolution out of your classes or code, and isolated to one place. For a fully fledged example, check out qissues.