How to get a document from Id gotten from another document angularFirestore

Question

I amb having a problem trying to get information from one document inside the other document, the one I need because it has the property Id.

On the following img, I can access to my diets collection and get my specific document, but then I am not able to 'come back' and get my info ID:

Then, my structure of users is the following:

Once I exposed my problem, I'll show you the code where I am not able to continue:

commentsDietC: AngularFirestoreDocument<any>;
commentsDiet : Observable<any>;

 this.commentsDietC = db.doc<any>('diets/'+this.diet.idDiet);
 this.commentsDiet = this.commentsDietC.snapshotChanges()
 .map(actions => {
  if(actions.payload.data()){
    if(actions.payload.data().hasOwnProperty('commentsDiet')){

      /*HERE is where I should try to get the displayName and PhotoUrl from 
      the other document*/
      return actions.payload.data().commentsDiet;
     }
  }

});

Any help would be really appreciated it.

Answer 1

I think you're looking for something like this:

this.commentsDiet = this.commentsDietC.snapshotChanges()
 .map(actions => {
  var data = actions.payload.data();
  if(data){
    if(data.hasOwnProperty('commentsDiet')){
      data.commentsDiet.forEach(comment => {
        var userDocRef = firebase.firestore().doc('users/'+comment.idUser);
        userDocRef.get().then(userDoc => {
          console.log(userDoc.data().displayName);
        });
      });
    }
  }    
});

So once you've determined that there are comments, this code loops over the comments, and then gets the user for each comment.