post.component.ts

import { GetPostGQL, Post } from './generated/graphql';

@Component({...})
export class PostComponent {
  @Input() postId: string;
  post: Observable<Post>;  
  
  constructor(
   private getPostGQL: GetPostGQL
  ) {}
  
  ngOnInit() {
    this.post = this.getPostGQL
      .watch({ id: this.postId })
      .valueChanges
      .pipe(
        map(result => result.data.post)
      );
  }
}