Requests as Promises

The observable returned by Angular http client can be converted it into a promise.

We recommend using observables over promises. By converting to a promise you will be lose the ability to cancel a request and the ability to chain RxJS operators.
  1. import { Http } from '@angular/http';
  2. import { Injectable } from '@angular/core';
  3. import 'rxjs/add/operator/map';
  4. import 'rxjs/add/operator/toPromise';
  6. @Injectable()
  7. export class SearchService {
  9.   constructor(private http: Http) {}
  11.   search(term: string) {
  12.     return this.http
  13.       .get(`https://api.spotify.com/v1/search?q=${term}&type=artist`)
  14.       .map((response) => response.json())
  15.       .toPromise();
  16.   }
  17. }

We would then consume it as a regular promise in the component.

  1. @Component({ /* ... */ })
  2. export class AppComponent {
  3.     /* ... */
  5.     search() {
  6.         this.searchService.search(this.searchField.value)
  7.           .then((result) => {
  8.         this.result = result.artists.items;
  9.       })
  10.       .catch((error) => console.error(error));
  11.     }
  12. }

原文: https://angular-2-training-book.rangle.io/handout/http/requests_as_promises.html