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我该怎么做才能让解析器等到它从 API 获取图像。现在，Angular 等到收到数据，显示页面，然后尝试获取帖子的图像。

@Injectable()
export class DataResolverService implements Resolve<any> {
  constructor(
    private router: Router,
    private API: ApiService
  ) {}

  resolve(
    route: ActivatedRouteSnapshot,
    state: RouterStateSnapshot
  ): Observable<any> | Observable<never> {
    return this.API.getPostById(route.params.id).pipe(
      map(response => {
        if (response["images"]) {
          const images = [];
          response["images"].forEach(image => {
            this.API.getImageById(image.id).subscribe(
              (img: any) => {
                const imageObject = {
                  url: window.URL.createObjectURL(img),
                };
                images.push(imageObject);
              }
            );
          });
          response["images"] = images;
          return response;
        }

        return response;
      })
    );
  }
}
4

2 回答 2

2

尝试：

@Injectable()
export class DataResolverService implements Resolve<any> {
  constructor(
    private router: Router,
    private API: ApiService
  ) {}

  resolve(
    route: ActivatedRouteSnapshot,
    state: RouterStateSnapshot
  ): Observable<any> | Observable<never> {
    return this.API.getPostById(route.params.id).pipe(
      switchMap(response => { // change this into a switchMap
        if (response["images"]) {
          return combineLatest(
            // combine all of the request for the images
            ...response["images"].map(image => this.API.getImageById(image.id)),
          ).pipe(
            map(images => images.map(image => ({ url: window.URL.createObjectURL(image) })),
            map(images => ({ response: images })), // This map may be unnecessary
          );
        } else {
         return of([]);
        }
      })
    );
  }
}

那应该让你开始。您的方法的问题是您订阅了内部可观察对象，我不认为路由解析器正在等待它。

于 2020-03-05T12:53:51.657 回答
0

您在异步方法“this.API.getImageById(image.id)”解析之前返回“响应”。在返回之前，您必须等待所有异步迭代结束。有一些选项可以做到这一点，这是选项：

return this.API.getPostById(route.params.id).pipe(
      map(async response => {
        if (response["images"]) {
          const images = [];
          response["images"].forEach(image => {
           await this.API.getImageById(image.id).then(
              (img: any) => {
                const imageObject = {
                  url: window.URL.createObjectURL(img),
                };
                images.push(imageObject);
              }
            );
          });
          response["images"] = images;
          return response;
        }

        return response;
      })
    );
于 2020-03-05T12:51:16.767 回答