Question

我想使用BehaviorSubject取消订阅另一个使用takeUntil的Observable。当我使用takeUntil订阅Observable时，它似乎立即取消订阅。此代码适用于Subject，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

当然，您可以使用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
    }

Btw：从RxJS> = 5.5开始，您可以在我的示例中使用pipe。另外，您可以在结尾处用$来命名您的可观察对象，以便其读取“ status1stream”

Answer 2

您也可以使用过滤器。

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 ");

Answer 3

BehaviorSubject将具有初始值。因此，只要您的takeUntil内部订阅，它就会释放其初始值。见（这里）[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).

改为使用PublishSubject。

Answer 4

您在takeWhile之后:( 因为takeUntil没有采用谓词）。

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

RxJs - 我可以使用带有takeUntil的BehaviorSubject吗？

4 个答案: