Question

我正在使用Angular 5，我正在使用如下的BehaviorSubject（Rxjs版本是＆＃34; rxjs＆＃34;：＆＃34; ^ 5.1.0＆＃34;，正如我在package.json文件中提到的那样）

ngOnInit() {
    this.getConfirmReturnValue();
}

getConfirmReturnValue() {
    this.confirmService.getReturnValue()
        .takeWhile(() => this.alive = true)
        .subscribe(
            suc => {
                console.log('return value::', suc);
                if (suc != 0 && suc.hasOwnProperty('returnValue')) {
            this.deleteLanguage(suc); }
        });
 }

在onDestroy方法中我取消订阅如下

ngOnDestroy() {
    this.alive = false;
}

但我在浏览器控制台中收到以下错误

at SafeSubscriber._next (languages-view.component.ts:143)
    at SafeSubscriber.webpackJsonp.../../../../rxjs/Subscriber.js.SafeSubscriber.__tryOrUnsub (Subscriber.js:239)
    at SafeSubscriber.webpackJsonp.../../../../rxjs/Subscriber.js.SafeSubscriber.next (Subscriber.js:186)
    at Subscriber.webpackJsonp.../../../../rxjs/Subscriber.js.Subscriber._next (Subscriber.js:126)
    at Subscriber.webpackJsonp.../../../../rxjs/Subscriber.js.Subscriber.next (Subscriber.js:90)
    at TakeWhileSubscriber.webpackJsonp.../../../../rxjs/operators/takeWhile.js.TakeWhileSubscriber.nextOrComplete (takeWhile.js:84)
    at TakeWhileSubscriber.webpackJsonp.../../../../rxjs/operators/takeWhile.js.TakeWhileSubscriber._next (takeWhile.js:79)
    at TakeWhileSubscriber.webpackJsonp.../../../../rxjs/Subscriber.js.Subscriber.next (Subscriber.js:90)
    at BehaviorSubject.webpackJsonp.../../../../rxjs/Subject.js.Subject.next (Subject.js:55)

Answer 1

takeWhile运算符的回调函数要求您返回布尔值。现在你正在返回undefined，因为this.alive = true只是一个赋值，而这本身并没有返回任何内容。

所以你应该这样做：

.takeWhile(() => this.alive) // or this.alive === true

请注意，仅当takeWhile发出值时才会调用this.confirmService.getReturnValue()，因此当组件被销毁时，它可能不会立即意味着链也被处理掉。

Answer 2

我删除了takeWhile（ - ）并在下面做了，它解决了我的问题

getConfirmReturnValue() {
      this.subscription1 = this.confirmService.getReturnValue()
        .subscribe(
            suc => {
                console.log('return value::', suc);
                if (suc != 0 && suc.hasOwnProperty('returnValue')) {
            this.deleteLanguage(suc); }
        });
    }

ngOnDestroy() {
        this.subscription1.unsubscribe();
    }

Answer 3

您可以使用以下代码取消订阅ngOnDestroy。

getConfirmReturnValue() {
this.var = this.confirmService.getReturnValue()
    .takeWhile(() => this.alive = true)
    .subscribe(
        suc => {
            console.log('return value::', suc);
            if (suc != 0 && suc.hasOwnProperty('returnValue')) {
        this.deleteLanguage(suc); }
    });} 

ngOnDestroy() {
   this.var.unsubscribe();}

无法取消订阅Angular 5 Applicaiton中的BehaviorSubject

3 个答案: