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See an interesting picture about Rx learning, want to know the learning curve of learning Rx? No, it's the cliff!

We can create Observable objects directly through Rx's Observer.

However, using this approach is often complicated, and in specific scenarios, we can directly use the specific Subject provided by Rx to implement Observable. These specific Subject are a mixture of topics and subscribers, and we can directly use such an object to publish information and subscribe to data streams.

1. Subject

General-purpose Subject can be subscribed to, and you can see from the name that it is a topic, so it can be used to publish information directly. If you need to implement a common theme, it is the ideal choice.

Mode of use:

How to publish information:

OnNext (value)

Publish a new value to the data stream.

OnCompleted ()

The data flow terminates.

OnError (error)

Release an exception.

Examples of use:

Var subject = new Rx.Subject (); var subscription = subject.subscribe (function (x) {console.log ('Next:' + x.toString ());}, function (err) {console.log ('Error:' + err);}, function () {console.log ('Completed');}); subject.next (42); / / > Next: 42subject.next (56) / / = > Next: 56subject.completed (); / / = > Completed

See Also:

Https://github.com/Reactive-Extensions/RxJS/blob/master/doc/api/subjects/subject.md

2. AsyncSubject

Cache up to the last value of completed (). All subscribers will receive the same last value.

Note that there can be only one value, and after completed (), no new values can be published. And all subscribers can only get the last value.

Mode of use:

The stream must be completed with completed (), and the subscriber will not get the last value until after completed ().

Examples of use:

Var subject = new Rx.AsyncSubject (); var I = 0politic var handle = setInterval (function () {subject.onNext (I); if (+ + I > 3) {subject.onCompleted (); clearInterval (handle);}}, 500); var subscription = subject.subscribe (function (x) {console.log ('Next:' + x.toString ()) }, function (err) {console.log ('Error:' + err);}, function () {console.log ('Completed');}); / / = > Next: 3DB / = > Completed

Legend

See also: https://github.com/Reactive-Extensions/RxJS/blob/master/doc/api/subjects/asyncsubject.md

3. BehaviorSubject

Consider this if you want the subscriber to get the current last value, but a new value may be provided later.

The last published data is cached, and new subscribers can receive the last published value, as well as new values released later.

It can directly set an initial value. If you don't need an initial value, you can consider using ReplaySubject.

Usage: BehaviorSubject (initialValue)

Provide the initial value in the constructor.

GetValue ()

Gets the current value, or throws an exception, and after calling completed (), the last value is retained. After error (), a specific exception is always thrown.

Use the example

/ * Initialize with initial value of 42 * / var subject = new Rx.BehaviorSubject (42); var subscription = subject.subscribe (function (x) {console.log ('Next:' + x.toString ());}, function (err) {console.log ('Error:' + err);}, function () {console.log ('Completed');}); / / > Next: 42subject.next (56) / / = > Next: 56subject.completed (); / / = > Completed

Legend See also:

Https://github.com/Reactive-Extensions/RxJS/blob/master/doc/api/subjects/behaviorsubject.md

4. ReplaySubject

It can be used to cache the last n pieces of data in the stream, and after the new observer is registered, the cached data is published directly to the new observer.

Instructions for use:

When constructing the ReplaySubject object, configure the number of cached data elements and the time window.

ReplaySubject ([bufferSize], [windowSize], [scheduler])

Use specific cache sizes, time windows, and schedulers to create ReplaySubject object instances.

Arguments

[bufferSize = Number.MAX_VALUE] (Number): Maximum element count of the replay buffer.

[windowSize = NUMBER.MAX_VALUE] (Number): Maximum time length of the replay buffer.

[scheduler = Rx.Scheduler.currentThread] (Scheduler): Scheduler the observers are invoked on.

Use the example

Var subject = new Rx.ReplaySubject (2 / * buffer size * /); subject.next ('a'); subject.next ('b'); subject.next ('c'); var subscription = subject.subscribe (function (x) {console.log ('Next:' + x.toString ());}, function (err) {console.log ('Error:' + err) }, function () {console.log ('Completed');}); / / = > Next: bstroke / = > Next: csubject.next (' d'); / / = > Next: d

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