API option to get only existing service

[y-nk]

Hello,

In a container, I'd like to know how to getAll only already instantiated singletons. The usecase is the following:

// services.ts

@injectable('Singleton')
class DB {
  // ...
  async close()
}

@injectable('Singleton')
class MQ {
  // ...
  async close()
}

@injectable('Singleton')
class SomeRepo {
  constructor(@inject(DB) db: DB) {}
}

// main.ts
import { DB, MQ, SomeRepo } from './services'

const services = [DB, MQ, SomeRepo]
const container = new Container()

app.on('ready', () => {
  for (const service of services) {
    container.bind(service).toSelf()
  
    if (service.prototype.close) {
      // See: https://github.com/inversify/monorepo/issues/1147#issuecomment-3400365381
      container.bind('onClose').toResolvedValue(() => container.getAsync(service))
    }
  }
})

app.get('/foo', async (req, res) => {
  const repo = await container.getAsync(SomeRepo)
  return repo...blah()
})

// container.getAsync(MQ) ← never ever in the code

app.on('close', () => {
  // Here, the container may or may not have an instance of SomeRepo and/or DB
  // but never have instantiated MQ anywhere. How to retrieve the list of only
  // existing singleton matching that service identifier?
  const services = container.getAll<{ close: () => Promise<void> }>('onClose')

  for (const service of services) {
    await service.close()
  }
})

Thank you for your time and guidance 🙏

[y-nk]

Workaround note to achieve the same effect without explicit API:

1. add @preDestroy() instead of service.prototype.close detection with additional binding
2. call container.unbindAll()

I'm marking this as answered because it's the true way of using the framework but i'm still genuinely curious on how to achieve pulling existing singleton otherwise

[notaphplover]

Hey @y-nk, as you correctly suggested, pre destroy mechanism is probably the best way to go. I wrote a plugin for this specific case you might like to consider: https://github.com/inversify/monorepo/tree/main/packages/container/libraries/plugin-dispose

[y-nk]

thank you. i will have a close look at your plugin code as i could learn useful structures with inversify.

have a nice day 🙏

[notaphplover]

Thanks man, you too. If you have an issue using the plugin just create an issue and I'll look into it 🙂