Angular error TS2322 arises when attempting to assign a type of 'Observable<{}>' with the share() operator

Currently diving into Angular 5, I've been exploring the Observable/Observer pattern to facilitate event sharing and data changes among subscribers.

Below is a snippet of the code in question:

...
@Injectable()
export class NidoService {
  ...
  event$: Observable<StrutturaDto[]>;
  private _observer: Observer<any>;

  event_dettaglio$: Observable<Struttura>;
  private _observer_dettaglio: Observer<any>;

  constructor() {
     this.event$ = new Observable(observer => this._observer = observer).share();
     this.event_dettaglio$ = new Observable(observer => this._observer_dettaglio = observer).share();
  }
  ...
}

Encountering challenges when trying to compile the application using ng build, errors appear on the lines within the constructor as follows:

ERROR in src/app/services/nido.service.ts(28,7): error TS2322: Type 'Observable<{}>' is not assignable to type 'Observable<StrutturaDto[]>'.
Type '{}' is not assignable to type 'StrutturaDto[]'.
Property 'includes' is missing in type '{}'.
src/app/services/nido.service.ts(29,7): error TS2322: Type 'Observable<{}>' is not assignable to type 'Observable<Struttura>'.
Type '{}' is not assignable to type 'Struttura'.
Property 'idStruttura' is missing in type '{}'.

In development mode, everything seems fine, but building becomes impossible without resolving these issues. How can I modify those specific lines of code?

Answer №1

To ensure accurate observation, it is important to define the type of observable:

this.event$ = new Observable<StrutturaDto[]>(observer => this._observer = observer).share();

Additionally,

this.event_dettaglio$ = new Observable<Struttura>(observer => this._observer_dettaglio = observer).share();

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