groupBy<S> method
inherited
The GroupBy operator divides an Observable that emits items into
an Observable that emits GroupByObservable,
each one of which emits some subset of the items
from the original source Observable.
GroupByObservable acts like a regular Observable, yet
adding a 'key' property, which receives its Type and value from
the grouper Function.
All items with the same key are emitted by the same GroupByObservable.
Implementation
Observable<GroupByObservable<T, S>> groupBy<S>(S grouper(T value)) =>
transform(GroupByStreamTransformer<T, S>(grouper));