RxJs - 我可以将 BehaviorSubject 与 takeUntil 一起使用吗？

Question

我想使用 BehaviorSubject 使用 takeUntil 取消订阅另一个 Observable。当我用 takeUntil 订阅 Observable 时，它似乎立即取消订阅。此代码适用于主题，但我想要一个初始值集。

我正在使用 rxjs 5.5.6

//MyService1
class Observable1 {
  status1: BehaviorSubject<boolean> = new BehaviorSubject<boolean>(false);

  displayStatus1(val: boolean) {
    this.status1.next(val)
  }
}

//MyService2
class Observable2 {
  status2: BehaviorSubject<boolean> = new BehaviorSubject<boolean>(false);

  displayStatus2(val: boolean) {
    this.status2.next(val)
  }
}

//MyComponent
status: boolean;

constructor(private myService1: MyService1, private myService2: MyService2) {
   this.subscribeToObservable1();
   this.subscribeToObservable2();
}

subscribeToObservable1() {
  this.myService1.status1.subscribe((val: boolean) => {
    console.log('val: ', val);
  }
}

subscribeToObservable2() {
  this.myService2.status2
    .takeUntil(this.myService1.status1)
    .subscribe((val: boolean) => {
      this.status = val;
    }
}

Answer 1

您在 takeWhile 之后：（因为 takeUntil 不采用谓词）。

var bs = new Rx.BehaviorSubject<boolean>(false); //create beahviour subject
const source = Rx.Observable.interval(1000);     //create observable
// take from obs while , behaviour subject not emitting true
const example = source.takeWhile ((a)=>bs.value!=true); 
const subscribe = example.subscribe(val => console.log(val));

setTimeout(()=>bs.next(true),3000); //make the BehaviorSubject emit true and stop.

http://jsbin.com/yaditucija/1/edit?js,console

Answer 2

BehaviorSubject 将具有初始值。因此，一旦您的 takeUntil 内部订阅它，它就会释放其初始值。请参阅（此处）[http://reactivex.io/documentation/subject.html]

When an observer subscribes to a BehaviorSubject, it begins by emitting the item most recently emitted by the source Observable (or a seed/default value if none has yet been emitted) and then continues to emit any other items emitted later by the source Observable(s).

改用 PublishSubject。

Answer 3

当然可以，只需使用 skip():

跳过第一个初始值

this.status2$
    .pipe(
        takeUntil(
           this.status1$.pipe(skip(1))
        ),
    )
    .subscribe((val: boolean) => {
         // I execute until status1$ emits
    }

顺便说一句：从 RxJS >= 5.5 开始，您可以像我的示例一样使用 pipe。你也可以在末尾用 $ 命名你的 observables，所以它显示为 "status1stream"

Answer 4

你也可以使用过滤器。

const source = new Subject();
const destory$ = new BehaviorSubject<boolean>(false);
source
  .pipe(takeUntil(destory$.pipe(filter((v: boolean) => v))))
  .subscribe(resp => {
    console.log("resp", resp);
  });

source.next("hello");

source.next("hello2");
destory$.next(true);
destory$.complete();
source.next("hello 3 ");

RxJs - 我可以将 BehaviorSubject 与 takeUntil 一起使用吗？

RxJs - Can I use a BehaviorSubject with takeUntil?

javascript

rxjs5

behaviorsubject