observable-defer

Procedural object for creating a lightning fast observable.

observable-defer is a procedural means of creating Most.js streams, which are a very fast implementator of the Observable specification. It works like the well-known Promise.defer(), creating a top level object with the publish methods (next, error (non terminal), and complete to defer's resolve and reject methods) and the observable these methods publish into (versus defer's promise).

Background

observable-defer was created to be an easy yet secure way of creating a very high performance observable stream, based on most.js.

Existing options for creating most streams procedurally were perceived as having significant usability conerns:

most-subject is very similar in nature, creating an object with publish methods on it. However rather than have a observable property attached, the subject itself is also the stream, making it difficult to use securely. Second, most-subject's implementation brings in most-multicast, which may or may not be desired for all use cases.

*most-create has an interface more closely matching the Promise constructor. Lacking a good Promise.defer equivalent alone was a cause for observable-defer. Further, unlike the Promise constructor, the create constructor is run lazily (in the manner of laissez-bird), when the observer is first observed, which makes trying to lift publish methods out of the constructor an interesting problem.

observable-defer is designed to provide immediate access to publish methods and the outputting observable, in an extremely fast manner.

Usage

var obs= ObservableDefer()
obs.next(0) // ignored! no one observing the observable yet.
obs.observable.forEach(console.log).then(console.log.bind(null, "done")) // observe the observable
obs.next(1) //=> 1
obs.next(2) //=> 2
obs.complete() //=> done

Notes

Note that while the observable-defer object immediately has publish methods, data passed to them will be dropped until the observable becomes observed. Check the observed property or attach an .onObserved handler to the object to check or see when the observable is observed.