Angular 4 将服务响应值传递给多个组件

Question

我需要将一个 http 响应值传递给多个组件。

我的主页组件 html 是

<app-featured></app-featured>
<app-filter></app-filter>
<app-business></app-business>

服务文件data-video.service

getPosts() {
     return this.http.get('http://grace-controls.com/mind-grid/mind_select.php')
     .map(res=>res.json())
   }

featured.component.ts

特色组件是一个光滑的 slider

ngOnInit() {
    this.dataServices.getPosts().subscribe((posts)=>{
          this.slides.splice(0, 1);
          for(let i=0; i<posts.length;i++) {
            this.slides.push({img:posts[i].image_url});
          }
        })
}
slides = [{img:''}];

business.component.ts

    ngOnInit() {
    //Here I have to request the same data service method or any common object access values here?
      }

如何获取并打印业务组件中的值？。哪种方法最可取？我是 Angular 的初学者，请帮助我？

Answer 1

我建议您创建 BehaviorSubject 以在本地管理您的帖子集合。

首先要做的是像这样创建模型:

/**
 * Strong type each item of your posts api.
 */
export class PostModel {
  id: string;
  title: string;
  descreption: string;
  image_url: string;
  video_id: string;
  country: string;
  language: string;
  company: string;
  date: string;
  clap: string;
  views: string;
  username: string;
}

然后你的服务看起来像这样:

@Injectable()
export class PostService {
  // Should be private and expose by magic getter, present bellow.
  private _posts$ : BehaviorSubject<PostModel[]>; 

  constructor(private http: HttpClient) {
    // We init by empty array, this means if you subscribe before ajax answer, you will receive empty array, then be notify imediatly after request is process.
    this._posts$ = new BehaviorSubject([]);
    // Because this data is mandatory, we ask directly from constructor.
    this.loadPost();
  }

  private loadPost() {
    this
    .http
    .get('http://grace-controls.com/mind-grid/mind_select.php')
    .pipe(map(res => (res as PostModel[]))) // We strong type as PostModel array
    .subscribe(posts => this._posts$.next(posts)); // we push data on our internal Observable.
  }
  // Magic getter who return Observable of PostModel array.
  get posts$() : Observable<PostModel[]> {
    return this._posts$.asObservable();
  }
  // magic getter who return Observable of {img:string} array.
  get slides$(): Observable<Array<{img:string}>> {
    return this._posts$.pipe(map(posts => {
        return posts.map(post => {
          return {
            img: post.image_url
          }
        });
    }));
  }
}

然后您可以在您的应用程序的任何地方使用您的数据，只需执行以下操作:

export class AppComponent implements OnInit{

  constructor(private postService: PostService) { }

  ngOnInit() {
    this.postService.posts$.subscribe(posts => {
      console.log(posts);
    });
    // OR
    this.postService.slides$.subscribe(slides => {
      console.log(slides);
    });
  }
}

详细信息:BehaviorSuject 必须使用默认值进行初始化，然后当消费者订阅它时，他将始终返回最后发出的值。

样本:Online sample 不幸的是，ajax 请求从您的 url 中抛出错误，因为您的服务器未通过 https。无论如何，此在线示例已准备好完整代码以供检查。

__ 更新 __

我已经更新我的示例，评论 HttpCall 并将其替换为虚拟数据。