Blocking Observable Operators

David Gross edited this page Jan 12, 2015 · 49 revisions

This section explains the BlockingObservable subclass. A Blocking Observable extends the ordinary Observable class by providing a set of operators on the items emitted by the Observable that block.

To transform an Observable into a BlockingObservable, use the Observable.toBlocking( ) method or the BlockingObservable.from( ) method.

  • forEach( ) — invoke a function on each item emitted by the Observable; block until the Observable completes
  • first( ) — block until the Observable emits an item, then return the first item emitted by the Observable
  • firstOrDefault( ) — block until the Observable emits an item or completes, then return the first item emitted by the Observable or a default item if the Observable did not emit an item
  • last( ) — block until the Observable completes, then return the last item emitted by the Observable
  • lastOrDefault( ) — block until the Observable completes, then return the last item emitted by the Observable or a default item if there is no last item
  • mostRecent( ) — returns an iterable that always returns the item most recently emitted by the Observable
  • next( ) — returns an iterable that blocks until the Observable emits another item, then returns that item
  • latest( ) — returns an iterable that blocks until or unless the Observable emits an item that has not been returned by the iterable, then returns that item
  • single( ) — if the Observable completes after emitting a single item, return that item, otherwise throw an exception
  • singleOrDefault( ) — if the Observable completes after emitting a single item, return that item, otherwise return a default item
  • toFuture( ) — convert the Observable into a Future
  • toIterable( ) — convert the sequence emitted by the Observable into an Iterable
  • getIterator( ) — convert the sequence emitted by the Observable into an Iterator

This documentation accompanies its explanations with a modified form of "marble diagrams." Here is how these marble diagrams represent Blocking Observables:

see also:

Appendix: similar blocking and non-blocking operators

operator result when it acts on equivalent in Rx.NET
Observable that emits multiple items Observable that emits one item Observable that emits no items
Observable.first the first item the single item NoSuchElement firstAsync
BlockingObservable.first the first item the single item NoSuchElement first
Observable.firstOrDefault the first item the single item the default item firstOrDefaultAsync
BlockingObservable.firstOrDefault the first item the single item the default item firstOrDefault
Observable.last the last item the single item NoSuchElement lastAsync
BlockingObservable.last the last item the single item NoSuchElement last
Observable.lastOrDefault the last item the single item the default item lastOrDefaultAsync
BlockingObservable.lastOrDefault the last item the single item the default item lastOrDefault
Observable.single Illegal Argument the single item NoSuchElement singleAsync
BlockingObservable.single Illegal Argument the single item NoSuchElement single
Observable.singleOrDefault Illegal Argument the single item the default item singleOrDefaultAsync
BlockingObservable.singleOrDefault Illegal Argument the single item the default item singleOrDefault