How to ensure local array always contains latest data in Ionic / Angular app?

Ionic Framework Ionic Angular
1

In my Ionic / Angular app, a Conversation object contains an array of Message objects.

I am able to add Conversations , no problem using the below code. When I console.log this.conversations , all of the Conversations are displayed.

private _conversations = new BehaviorSubject<Conversation[]>([]);

get conversations() {
    return this._conversations.asObservable();
}

addConversation(mechanicId: string, message: string) {
    let generatedId;
    const newConversation = new Conversation(
      Math.random().toString(),
      [new Message(
        Math.random().toString(),
        message,
      )]
    );
    return this.http.post<{ name: string }>(
      'myUrl/conversations.json',
      { ...newConversation, id: null }
    ).pipe(
      switchMap(resData => {
        generatedId = resData.name;
        console.log('My Conversations', this.conversations);
        return this.conversations;
      }),
      take(1),
      tap(conversations => {
        newConversation.id = generatedId;
        this._conversations.next(conversations.concat(newConversation));
      })
    );
  }

However, when I try to update a Conversation (i.e. add a new Message to it), when I console.log this.conversations , I am only getting back the Conversation which I am updating:

addMessageToConversation(conversationId: string, message: string) {
    let updatedConversations: Conversation[];
    return this.conversations.pipe(
      take(1),
      switchMap((conversationToUpdate: any) => {
        conversationToUpdate.messages.push(
          new Message(
            Math.random().toString(),
            message,
            this.authService.userId,
            new Date(Date.now())
          )
        );
        console.log('Conversations after adding new message', this.conversations);
        // This only shows the Conversation I am looking @ currently. I want it to have all the latest Conversations & Messages, not just this one
        return this.http.put(
          `myUrl/conversations/${conversationId}.json`,
          { ...conversationToUpdate, id: null }
        );
      }), tap(() => {
        // this._conversations.next(updatedConversations); // dont't think this is doing what I want it to
      })
    );
  }

I want to get back all of the Conversations so that _conversations always contains the latest Conversations .

Can someone please tell me how I can ensure _conversations always contains all Conversations , rather than just the one who’s ID is passed into addMessageToConversation() ?

So if I add a new Conversation, it shows all Conversations in the console. But if I add a new Message to a Conversation, it only shows that Conversation in the console, while I want it to show all Conversations.