How do I register service cleanup?

export class PollingService extends Service<PollingService> {
  private _intervalId: ReturnType<typeof setInterval>;

  constructor() {
    super();
    this._intervalId = setInterval(() => this.poll(), 5000);
    this.registerCleanup(() => clearInterval(this._intervalId));
  }

  protected onDestroy(): void {
    // async/custom teardown logic goes here
  }
}

registerCleanup(fn) is protected — call it from inside your own service (typically the constructor) to queue teardown logic. There are two independent cleanup paths, and they run different things:

• dispose() — runs every queued registerCleanup callback, then clears the callback list and removes the instance from the singleton registry. This is wired automatically to window.beforeunload for every service instance; you never call it yourself.
• Service.destroy(MyService) / Service.destroyAll() — awaits and calls onDestroy() on the instance(s), then removes them from the registry. This does not run registerCleanup callbacks — only the onDestroy() hook. main.ts typically wires Service.destroyAll() to window.beforeunload at the app level, so in practice both paths can fire on unload, each covering a different kind of teardown.

Override onDestroy() for cleanup that needs to be async or explicitly triggered (e.g. from app shutdown logic), and use registerCleanup() for cleanup that should always run alongside every other service's, on page unload.

Test-only resets

MyService.testingReset();     // drops this class's instance from the registry
Service.testingResetAll();    // drops every instance

These are synchronous and run no cleanup at all — neither registerCleanup callbacks nor onDestroy(). They exist purely to reset singleton state between test cases; using them in application code would silently skip real cleanup and leak resources.

MyService.hasInstance(MyService); // boolean — has getInstance() been called yet?