使 Angular 解析器等待图像

Question

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 post.

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;
      })
    );
  }
}

Answer 1

您在异步方法 "this.API.getImageById(image.id)" 解析之前返回 "response"。您必须等待所有异步迭代结束才能返回。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;
      })
    );

Answer 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([]);
        }
      })
    );
  }
}

这应该可以帮助您入门。您的方法的问题是您订阅了内部可观察对象，我认为路由解析器没有在等待它。

使 Angular 解析器等待图像

Make Angular resolver wait for images

javascript

angular

typescript

angular-resolver