Use of rxjs withLatestFrom function

Question

Trying to execute the following code that is supposed to :

Retrieve a list of all the chats of a user
retrieve last message for all these chats
Retrieve recipients info for all these chats

Merge all together as an array in which each item is a combination of a chat, last message and recipient info

 this.msgService.getUserChatList(this.uid).do((chats) => {
    this.chats = [];
    if (!(chats.length > 0))
      this.loading = false;
    this.getLastMessages$ = this.getLastMessagesForChats(chats);
    this.getRecipients$ = this.getRecipientsForChats(chats);
}).switchMap( chats => Observable.from(chats) ).withLatestFrom(
   this.getLastMessages$,
   this.getRecipients$,
   (chat, lastMessages, recipients) => ({
     chat: chat,
     last: lastMessages[chat['id']],
     recipient: recipients[chat['id']]
    })
).subscribe( chats => {
  console.log('chats ', chats);
  this.chats.push(chats);
  this.loading = false;
});

Additional functions

getLastMessagesForChats(chats: any): Observable {
    let lastMessages$ = [];
    for (let chat of chats) {
      let obs = this.msgService.getLastMessage(chat.id)
        .map( last => ({chat: chat.id, last: last}) );
      lastMessages$[chat.id] = obs;
    }
    return Observable.from(lastMessages$).merge().toArray();
  }

  getRecipientsForChats(chats: any): Observable {
    let recipients$ = [];
    for (let chat of chats) {
      let obs = this.userService.getUserPublicInfo(chat.recipient)
        .map( recipient => ({chat: chat.id, recipient: recipient}) );
      recipients$[chat.id] = obs;
    }
    return Observable.from(recipients$).merge().toArray();
  }

I am getting the following error

Uncaught (in promise): TypeError: Cannot read property 'subscribe' of undefined
    TypeError: Cannot read property 'subscribe' of undefined

I cannot find what is going wrong... I tried to reproduce in the following JSBIN

Any idea?

Use of rxjs withLatestFrom function

1 Answers