Kako deluje HttpClient?

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**`HttpClient`** je vgrajena storitev Angular za pošiljanje HTTP zahtevkov. Vrača **Observables** (ne Promises), se integrira s RxJS operatorji in podpira tipizirane odgovore, prestreznike in obdelavo napak. ## Osnovna uporaba ```ts import { HttpClient } from "@angular/common/http"; import { Injectable } from "@angular/core"; @Injectable({ providedIn: "root" }) export class UserService { constructor(private http: HttpClient) {} getUsers() { return this.http.get("/api/users"); // typed: Observable } createUser(user: User) { return this.http.post("/api/users", user); // body as 2nd arg } deleteUser(id: number) { return this.http.delete(`/api/users/${id}`); } } ``` Generic (``) tipizira odgovor. Zahtevki so **leni** — sprožijo se le ob naročnini. ## Poraba v komponenti ```ts ngOnInit() { this.userService.getUsers().subscribe(users => this.users = users); } // or with the async pipe (no manual subscribe/unsubscribe): users$ = this.userService.getUsers(); // template:

``` ## Možnosti zahtevka: parametri, glave ```ts import { HttpParams, HttpHeaders } from "@angular/common/http"; this.http.get("/api/users", { params: new HttpParams().set("page", "1").set("limit", "10"), // ?page=1&limit=10 headers: new HttpHeaders({ Authorization: `Bearer ${token}` }), }); ``` ## Obdelava napak s RxJS ```ts import { catchError, retry } from "rxjs/operators"; import { of } from "rxjs"; this.http.get("/api/users").pipe( retry(2), // retry failed requests twice catchError(err => { console.error(err); return of([]); // fallback value, keep the stream alive }) ).subscribe(users => this.users = users); ``` Ker temelji na Observable, sestavljate ponovne poskuse, nadomestke, časovne limite in transformacije z operatorji. ## Prestreznniki obravnavajo prečne naloge ```text HTTP interceptors automatically attach auth tokens, log requests, handle errors globally, or show loading spinners — for ALL requests. ``` ## Zakaj je pomembno `HttpClient` je način, kako Angular aplikacije govorijo z backendi — tipiziran, na osnovi Observable in sestavljen s RxJS za ponovne poskuse/nadomestke/transformacije. Narava Observable (v primerjavi s fetch Promises) ga integrira s preostankom Angular (async pipe, operatorji, prestreznniki). Pознавање tipiziranih zahtevkov, možnosti, obdelave napak in parjenja s `async` cevjo pokriva praktično vse potrebe Angular pri pridobivanju podatkov.