Angular 2:从父组件中的http获取数据并在其上嵌套订阅

Question

我打算做这样的架构:

• 零件 store
• - 嵌套组件 book

in store- 我有一个服务调用,从服务中获取数据,我对结果进行订阅.就像在angular2 docs(http)中描述的那样.

我想在嵌套组件中使用这些数据:form(formBuilder),材料设计元素等.

哪种方式最好,这样做？我是angular2的新手.

商店:

book: IBook;

constructor(private bookService: BookService) { }

ngOnInit() {
    this.bookService.getBook('1')
        .subscribe((book) => {
            this.book = book;
        });
}

bookService的:

...

getBook (id): Observable<IBook> {
    return this.http.get(this.url + '/' + id)
        .map(this.extractData)
        .catch(this.handleError);
}

private extractData(res: Response) {
    let body = res.json();
    return body || { };
}

...

书:

@Input() book:IBook;

constructor() {}

ngOnInit() {
    /*How here can i subscribe on book http data get?, so that i can use async value in forms etc?*/
});

因为,如果我book在任何地方都使用async (不是formBuilder) - 一切正常,但是在父组件中加载数据之后,formBuilder需要更新值.我怎样才能做到这一点？

Answer 1

bookID将 传递给BookComponent并让BookComponent处理异步 http 进入 怎么样ngInit？

export class Book implements OnInit {
  @Input() bookID: number;
  private book: IBook;

  constructor(private bookService: BookService) {}

  ngOnInit() {
    this.bookService.getBook(this.bookID)
      .subscribe((book) => {
        this.book = book;
      });
  }
}

否则，您有一些选项，请参见https://angular.io/docs/ts/latest/cookbook/component-communication.html进行解释

我将简要强调我认为您可以使用的两种方法。

使用 ngOnChanges 拦截输入属性更改

export class Book implements OnChanges {
  @Input() book: IBook;
  ngOnChanges(changes: {[propKey: string]: SimpleChange}) {
    for (let propName in changes) {
       // handle updates to book
    }
  }
}

更多信息https://angular.io/docs/ts/latest/guide/lifecycle-hooks.html

家长和孩子通过服务进行交流

@Injectable()
export class BookService {
  books = new Subject<IBook>();

  getBook(id): Observable<IBook> {
    return this.http.get(this.url + '/' + id)
    .map(d => {
      let book = this.extractData(d);
      this.books.next(book);
      return book;
    })
    .catch(this.handleError);
  }
  ...
}

@Component({
  selector: 'book',
  providers: []
})
export class Book implements OnDestroy {
  book: IBook
  subscription: Subscription;

  constructor(private bookService: BookService) {
    this.subscription = bookService.books.subscribe(
      book => {
        this.book = book;
    });
  }

  ngOnDestroy() {
    this.subscription.unsubscribe();
  }
}

@Component({
  selector: 'store',
  providers: [BookService]
})
export class Store {
  book: IBook;

  constructor(private bookService: BookService) { }

  ngOnInit() {
    this.bookService.getBook('1')
        .subscribe((book) => {
            this.book = book;
        });
  }
}