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typescript - Are RxJS observables different to observables of other languages?

问题描述

I want to move data from one place, to another and consider to use an Observable. I know observables from other languages, but somehow I find them very confusing. Given is the example below from a tutorial:

const foo$ = new Observable(subscriber => {
  subscriber.next(42);
  subscriber.next(43);
});

Why does the definition of foo = ... contain the value(s)? If foo would be the observable that can be subscribed to, how are the values coming in dynamically? Why is this called like this? Shouldn't it be triggered like this:

const foo$ = new Observable();

foo.subscribe((data) => console.log(data));

foo.sendSomeData(3);

In my case I want to create an observable which one consumer subscribes to, and the other source simply pushes data.

标签： typescriptrxjs

解决方案

What you want is a subject or a behavior subject. A subject is both an observable and an observer so that it exposes it's next methods. The difference between the two is that a behavior subject stores the previously emitted value and new subscribers get that value on subscribing. Subscribers to a subject get a value the next time the next method is called.

const { Subject } = rxjs;

const obs$ = new Subject();

obs$.subscribe(val => { console.log(val); });

obs$.next('Hello');

setTimeout(() => { obs$.next('Later'); }, 1000);
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