get the ID of collection document from Firestore using Angularfire2 in ionic 3 [duplicate]

Answer 1

i changed the code to:

  this.itemsCollection = this.afs.collection('posts', ref => ref.orderBy('createdDate', 'desc'));
  this.items = this.itemsCollection.snapshotChanges().pipe(
    map(actions => actions.map(a => {
      const data = a.payload.doc.data() as Item;
      const id = a.payload.doc.id;
      return { id, ...data };
    }))
  );

and it worked perfectly.

Answer 2

This is because by using valueChanges() "all Snapshot metadata is stripped and just the method provides only the data", as explained in the doc.

You should use snapshotChanges(), see the doc here which says: "Why would you use it? - When you need a list of data but also want to keep around metadata."