The change of data in controller doesn't update automatically

If I tried this:

@Page({
  selector: 'pipes',
  changeDetection: 'ON_PUSH',
  templateUrl: 'build/pages/post/new-post.html'
})

then I got another error:

EXCEPTION: Invalid argument 'img/placeholder.png' for pipe 'AsyncPipe' in [thumbnail | async in NewPostPage@25:13]