Requests as Promises

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.

import { Http } from '@angular/http';
import { Injectable } from '@angular/core';
import 'rxjs/add/operator/map';
import 'rxjs/add/operator/toPromise';
@Injectable()
export class SearchService {
  constructor(private http: Http) {}
  search(term: string) {
    return this.http
      .get(`https://api.spotify.com/v1/search?q=${term}&type=artist`)
      .map((response) => response.json())
      .toPromise();
  }
}

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

@Component({ /* ... */ })
export class AppComponent {
    /* ... */
    search() {
        this.searchService.search(this.searchField.value)
          .then((result) => {
        this.result = result.artists.items;
      })
      .catch((error) => console.error(error));
    }
}

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