Observable (minn il-librerija RxJS) jirrappreżenta fluss ta' valuri fuq periodu ta' ħin li tista' tissoskrivi għaliha. Angular tuża RxJS b'mod wiesa' — talbiet HTTP, avvenimenti tar-router, formoli u EventEmitter huma kollha bbażati fuq Observable — allura t-tifhim tagħhom huwa essenzjali.
Promise: a SINGLE future value, eager, can't cancel
Observable: ZERO-to-MANY values over time, lazy (runs on subscribe), CANCELLABLE
Observable jistgħu jemittu valuri multipli, joħorġu biss meta tissoskrivi, u jistgħu jiġu annullati — jagħmilhom ideali għal avvenimenti, flussuri u HTTP li tista' trid tannulla.
import { HttpClient } from "@angular/common/http";
this.http.get<User[]>("/api/users").subscribe({
next: (users) => this.users = users, // each emitted value
error: (err) => console.error(err), // on error
complete: () => console.log("done"), // stream finished
});
Xejn ma jiġri sal-meta ma tkompli .subscribe() — l-Observable huwa lazy.
import { map, filter, debounceTime } from "rxjs/operators";
this.searchInput.valueChanges.pipe(
debounceTime(300), // wait for typing to pause
filter(text => text.length > 2), // ignore short queries
map(text => text.trim()), // transform
).subscribe(query => this.search(query));
Operatori (imqabbra ġewwa .pipe()) jittrasformaw il-fluss b'mod deklarattiv — debounce, filter, map, eċċ. — jissolvu b'eleganza problemi async komuni (bħall-ħlas dum tikteb).
import { Subscription } from "rxjs";
private sub = new Subscription();
ngOnInit() { this.sub = this.data$.subscribe(...); }
ngOnDestroy() { this.sub.unsubscribe(); } // ❗ prevent leaks
Il-sottoskrixjonijiet manuali għandhom jinddaħlu f' ngOnDestroy, jew jibqgħu jaħdmu wara l-komponent jirrocedu — tressief tal-memorja. Soluzzjonijiet komuni: il-async pipe (unsubscribe awtomatikament), jew takeUntilDestroyed().
<!-- ✅ the async pipe handles subscription AND cleanup for you -->
<li *ngFor="let user of users$ | async">{{ user.name }}</li>
Observable ta' RxJS huma intessuti ġol-Angular — ma tistax tuża HttpClient, formoli reattivi, jew ir-router mingħajr huma.
L-ħas tal-sottoskrixjoni, operatori u speċjalment annulment (jew l-użu tal-async pipe biex tevita l-ġestjoni manwali) huwa kritiku: dan huwa d-dest tal-qawwa ta' Angular għad-data asinkriona u wieħed mill-ħbieb l-aktar komuni tagħha (tressief minn sottoskrixjonijiet nisgħejħ).