I'm reading the rxjs manual, I'm a little confused about what's the difference between multicast and publish operators. They seem very similar.
I had the same question when reading http://reactivex.io/rxjs/manual/overview.html. So to make it clear, .publish() is just shorthand for .multicast(new Rx.Subject()) (and publishBehavior, publishLast, and publishReplay are similar but instantiate BehaviorSubject, AsyncSubject and ReplaySubject respectively).
They are indeed very similar, and they have a history that makes it even more confusing.
In simple terms, publish is a special case of multicast. publish always creates a new subject (and then pretty much uses multicast), whereas multicast uses the subject provided as an argument.
来源：https://stackoverflow.com/questions/38025123/whats-the-difference-between-publish-and-multicast-operator-in-rxjs-5