Property 'Update' does not exist on type 'Subscription' -- when trying to update Firebase data

Question

I'm trying to update Firebase data, and I'm running into the error "Property 'update' does not exist on type 'subscription'. I can console log the object, and it is indeed the object I want. I'm just not sure how I can update the object using the "subscribe" method on the observable.

import { Injectable } from '@angular/core';
import { Post } from './models/post.model';
import { AngularFireDatabase, FirebaseListObservable } from 'angularfire2/database';

@Injectable()
export class PostService {
  posts: FirebaseListObservable<any[]>;

  constructor(private database: AngularFireDatabase) {
    this.posts = database.list('posts');
  }

  getPosts(){
    return this.posts;
  }

  getPostById(postId: string){
    return this.database.object('posts/' + postId)
  }

  updatePost(localPost){
    var postInFirebase = this.getPostById(localPost.$key).subscribe(dataLastEmittedFromObserver => {
    postInFirebase = dataLastEmittedFromObserver
    console.log(postInFirebase)
    postInFirebase.update({content: localPost.content});
  });
};

  deletePost(localPostToDelete){
    let postInFireBase = this.getPostById(localPostToDelete.$key);
    postInFireBase.remove();
  }

  addPost(newPost: Post){
    this.posts.push(newPost)
  }

}

Answer 1

Try removing the var postInFirebase = from the subscribing line, because Observer.subscribe returns a Subscription object synchronously before the asynchronous callback is called. This will probably cause the TypeScript compiler to assign the type Subscription to your variable postInFirebase and throws a compilation error.

  updatePost(localPost){
    this.getPostById(localPost.$key).subscribe(dataLastEmittedFromObserver => {
      let postInFirebase = dataLastEmittedFromObserver
      console.log(postInFirebase)
      postInFirebase.update({content: localPost.content});
    });
  }

Or even better

  updatePost(localPost){
    this.getPostById(localPost.$key).subscribe(postInFirebase => {
      postInFirebase.update({content: localPost.content});
    });
  }

You seem confused by the asynchronous signature of Observables. When you call var value = Observable.subscribe((data) => { ...}); then value will be a Subscription and NOT the observed data, you can only access the observable data INSIDE the asynchronous callback. This makes me think that your deletePost method also won't work.