Angular 2 AsynPipe isn't working with an Observable

Question

I'm getting the following error:

EXCEPTION: Cannot find a differ supporting object '[object Object]' in [files | async in Images@1:9]

Here's the relevant part of the template:

<img *ngFor="#file of files | async" [src]="file.path">

Here's my code:

export class Images {
  public files: any; 
  public currentPage: number = 0;
  private _rawFiles: any;

  constructor(public imagesData: ImagesData) {
    this.imagesData = imagesData;  
    this._rawFiles = this.imagesData.getData()
        .flatMap(data => Rx.Observable.fromArray(data.files));
    this.nextPage();
  }

  nextPage() {
    let imagesPerPage = 10;
    this.currentPage += 1;
    this.files = this._rawFiles
                    .skip((this.currentPage - 1) * imagesPerPage)
                    .take(imagesPerPage);
    console.log("this.files:", this.files);                
  }
}

The console.log at the end shows that it's an observable:

this.imagesData.getData() return a regular RxJS observable from Angular's Http service, so why wouldn't async pipe work with it? Maybe the way I'm using flatMap() is wrong and it messes something up?

If I try to subscribe to this observable like that:

this.files = this._rawFiles
                .skip((this.currentPage - 1) * imagesPerPage)
                .take(imagesPerPage)
                .subscribe(file => {
                  console.log("file:", file);
                });

It prints a list of objects as expected:

Answer 1

Try with an Observable<File[]> instead:

this.files = this._rawFiles
         .skip((this.currentPage - 1) * imagesPerPage)
         .take(imagesPerPage)
         .map(file => [file])
         .startWith([])
         .scan((acc,value) => acc.concat(value))

This should require no manual code to subscribe and should work perfectly with your current template.

I do something very similar in this blog post.