未调用带有 ReplaySubject 的 forkJoin.subscribe

Question

我想创建一个 Observable，如果两个 ReplaySubject 实例都持有一个值，它就会触发。我尝试过这样的：

let v1 = new Rx.ReplaySubject();
let v2 = new Rx.ReplaySubject();

v1.next('X');

const combo = Rx.Observable.forkJoin(v1, v2)

combo.subscribe( arr => console.log(arr) )

v1.subscribe( s => console.log('v1', s) );
v2.subscribe( s => console.log('v2', s) );

v2.next('Y');

两者v1.subscribe都v2.subscribe被称为 ，但不是combo.subscribe。我有什么错吗？如何解决这个问题？

Answer 1

forkJoin仅当所有输入可观察值完成后，才会发出包含所有最后值的数组。如果您手动完成v1和v2,combo将发出：

let v1 = new rxjs.ReplaySubject();
let v2 = new rxjs.ReplaySubject();

v1.next('X');
v2.next('Y');
v2.next('Z'); // This additional value should demonstrate the idea of forkJoin

const combo = rxjs.forkJoin(v1, v2)
combo.subscribe( arr => console.log(arr) )

v1.complete();
v2.complete();

<script src="https://cdnjs.cloudflare.com/ajax/libs/rxjs/6.5.2/rxjs.umd.js"></script>

combineLatest如果您不希望内部可观察量完成，您可能会寻找：

let v1 = new rxjs.ReplaySubject();
let v2 = new rxjs.ReplaySubject();

v1.next('X');
v2.next('Y');

const combo = rxjs.combineLatest(v1, v2)
combo.subscribe( arr => console.log(arr) )

<script src="https://cdnjs.cloudflare.com/ajax/libs/rxjs/6.5.2/rxjs.umd.js"></script>