Angularfire take and map

Question

I have a little angular application (Angular 6) with angularfire2, now i want to select only one object, odered by date, i can get .take(1) or .map() but not together, how is that done?

I tried it with the following approche

    return this.db.list(this.BASE_PATH, ref => ref.orderByChild(this.PUBLISH_DATE).limitToLast(1)).snapshotChanges().pipe(take(1)).pipe(map(res => {
      return res.map(item => {
        console.log(item);
      });
    }));

Answer 1

take(n) only takes the first n emissions of the observable, not n items of the array emitted, see here for more information on the take operator.

You can just use map to sort/filter your array and return the desired value and then subscribe. Do something like this:

this.db.list(this.BASE_PATH, ref => ref.orderByChild(this.PUBLISH_DATE).limitToLast(1)).snapshotChanges()
      .pipe(map(arr => arr.sort((a, b) => b.date - a.date)[0]))
      .subscribe(item => {
        console.log(item);
      });

EDIT: This stackblitz might do a better job of showcasing it.