Readme.md

ts-system-components

This is a TypeScript library inspired by the Clojure(script) components lib by Stuart Sierra. Its job is to manage dependencies and lifecycle of statefull components in your application.

Install

npm i ts-system-components

or

yarn add ts-system-components

How to use

Each component of your system should implement the Component protocol. The Component protocol requires two methods, start and stop. These methods should be responsible for starting and stopping the component. They should return a Promise, and are usually used with async.

class Database implements Component {

  // Make this component require the Config component.
  private readonly config: Config
  constructor(config: Config) {
    this.config = config
  }

  async start() {
    this.connection = await createConnection()
  }

  async stop() {
    this.connection?.close()
  }

}

After defining your components, you can group them in a System, to describe the dependencies between them.

Your system should extend the System class, and each component should be a property annotated with the <YourSystemName>.Using() Decorator. This Decorator receives two arguments. The first is the dependencies of this component, this should be a list of other components declared in your system. The second is a builder function which will receive a map with the dependencies you requested, and should return a new instance of you component.

class MySystem extends System {

  @MySystem.Using([], () => new Config())
  config!: Config

  @MySystem.Using(['config'], ({config}) => new Database(config))
  database!: Database

}

To start the system you can just create a new instance and call .start() The library will ensure that each component is instantiated and started before being provided to the downstream components.

const system = new MySystem()
await system.start()

To stop the system, just call stop()

await system.stop()