博士TL;

对于这个问题，有两种可观察对象——有限值和无限值。

Observable产生有限(1)的值，而DOM事件监听器之类的Observable产生无限的值。

如果你手动调用subscribe(不使用async管道)，那么从无限个observable中取消订阅。

不要担心有限的，RxJs会处理它们的。

来源:

I tracked down an answer from Rob Wormald in Angular's Gitter here. He states (I reorganized for clarity and emphasis is mine): if its a single-value-sequence (like an http request) the manual cleanup is unnecessary (assuming you subscribe in the controller manually) i should say "if its a sequence that completes" (of which single value sequences, a la http, are one) if its an infinite sequence, you should unsubscribe which the async pipe does for you Also he mentions in this YouTube video on Observables that "they clean up after themselves..." in the context of Observables that complete (like Promises, which always complete because they are always producing one value and ending - we never worried about unsubscribing from Promises to make sure they clean up XHR event listeners, right?) Also in the Rangle guide to Angular 2 it reads In most cases we will not need to explicitly call the unsubscribe method unless we want to cancel early or our Observable has a longer lifespan than our subscription. The default behavior of Observable operators is to dispose of the subscription as soon as .complete() or .error() messages are published. Keep in mind that RxJS was designed to be used in a "fire and forget" fashion most of the time. When does the phrase "our Observable has a longer lifespan than our subscription" apply? It applies when a subscription is created inside a component which is destroyed before (or not 'long' before) the Observable completes. I read this as meaning if we subscribe to an http request or an Observable that emits 10 values and our component is destroyed before that http request returns or the 10 values have been emitted, we are still OK! When the request does return or the 10th value is finally emitted the Observable will complete and all resources will be cleaned up. If we look at this example from the same Rangle guide we can see that the subscription to route.params does require an unsubscribe() because we don't know when those params will stop changing (emitting new values). The component could be destroyed by navigating away in which case the route params will likely still be changing (they could technically change until the app ends) and the resources allocated in subscription would still be allocated because there hasn't been a completion. In this video from NgEurope Rob Wormald also says you do not need to unsubscribe from Router Observables. He also mentions the http service and ActivatedRoute.params in this video from November 2016. The Angular tutorial, the Routing chapter now states the following: The Router manages the observables it provides and localizes the subscriptions. The subscriptions are cleaned up when the component is destroyed, protecting against memory leaks, so we don't need to unsubscribe from the route params Observable. Here's a discussion on the GitHub Issues for the Angular docs regarding Router Observables where Ward Bell mentions that clarification for all of this is in the works.

我在NGConf上和Ward Bell讨论过这个问题(我甚至给他看了这个答案，他说他是正确的)，但他告诉我Angular的文档团队有一个解决这个问题的方案，但还没有发表(尽管他们正在努力让它得到批准)。他还告诉我，我可以在即将到来的官方推荐中更新我的SO答案。

接下来我们应该使用的解决方案是添加一个私有ngUnsubscribe = new Subject<void>();字段到所有在类代码中有.subscribe()调用observable的组件。

然后调用这个。ngunsubscribe .next();this.ngUnsubscribe.complete ();在ngOnDestroy()方法中。

秘密武器(正如@metamaker已经提到的)是在我们的每个.subscribe()调用之前调用takeUntil(this.ngUnsubscribe)，这将确保所有订阅在组件被销毁时被清除。

例子:

import { Component, OnDestroy, OnInit } from '@angular/core';
// RxJs 6.x+ import paths
import { filter, startWith, takeUntil } from 'rxjs/operators';
import { Subject } from 'rxjs';
import { BookService } from '../books.service';

@Component({
    selector: 'app-books',
    templateUrl: './books.component.html'
})
export class BooksComponent implements OnDestroy, OnInit {
    private ngUnsubscribe = new Subject<void>();

    constructor(private booksService: BookService) { }

    ngOnInit() {
        this.booksService.getBooks()
            .pipe(
               startWith([]),
               filter(books => books.length > 0),
               takeUntil(this.ngUnsubscribe)
            )
            .subscribe(books => console.log(books));

        this.booksService.getArchivedBooks()
            .pipe(takeUntil(this.ngUnsubscribe))
            .subscribe(archivedBooks => console.log(archivedBooks));
    }

    ngOnDestroy() {
        this.ngUnsubscribe.next();
        this.ngUnsubscribe.complete();
    }
}

注意:重要的是将takeUntil操作符添加为最后一个操作符，以防止操作符链中中间可观察对象的泄漏。

最近，在《Angular冒险》的一集中，Ben Lesh和Ward Bell讨论了如何/何时取消组件中的订阅。讨论大约在1:05:30开始。

Ward提到“现在有一个可怕的takeUntil dance，它需要很多机器”，Shai Reznik提到“Angular可以处理一些订阅，比如http和路由”。

作为回应，Ben提到现在正在讨论允许可观察对象钩子到Angular组件的生命周期事件中，Ward建议组件可以订阅一个生命周期事件的可观察对象，以便知道什么时候完成维护为组件内部状态的可观察对象。

也就是说，我们现在最需要解决方案，所以这里有一些其他的资源。

A recommendation for the takeUntil() pattern from RxJs core team member Nicholas Jamieson and a TSLint rule to help enforce it: https://ncjamieson.com/avoiding-takeuntil-leaks/ Lightweight npm package that exposes an Observable operator that takes a component instance (this) as a parameter and automatically unsubscribes during ngOnDestroy: https://github.com/NetanelBasal/ngx-take-until-destroy Another variation of the above with slightly better ergonomics if you are not doing AOT builds (but we should all be doing AOT now): https://github.com/smnbbrv/ngx-rx-collector Custom directive *ngSubscribe that works like async pipe but creates an embedded view in your template so you can refer to the 'unwrapped' value throughout your template: https://netbasal.com/diy-subscription-handling-directive-in-angular-c8f6e762697f

我在Nicholas博客的评论中提到，过度使用takeUntil()可能是一个信号，表明您的组件试图做太多事情，应该考虑将现有组件分离为功能组件和演示组件。然后你可以|将Feature组件的Observable异步到Presentational组件的Input中，这意味着在任何地方都不需要订阅。在这里阅读更多关于这种方法的信息。

对于每一个订阅，你都需要取消订阅。Advantage =>以防止状态变得过于沉重。

例如: 在组件1中:

import {UserService} from './user.service';

private user = {name: 'test', id: 1}

constructor(public userService: UserService) {
    this.userService.onUserChange.next(this.user);
}

在服务:

import {BehaviorSubject} from 'rxjs/BehaviorSubject';

public onUserChange: BehaviorSubject<any> = new BehaviorSubject({});

于component2:

import {Subscription} from 'rxjs/Subscription';
import {UserService} from './user.service';

private onUserChange: Subscription;

constructor(public userService: UserService) {
    this.onUserChange = this.userService.onUserChange.subscribe(user => {
        console.log(user);
    });
}

public ngOnDestroy(): void {
    // note: Here you have to be sure to unsubscribe to the subscribe item!
    this.onUserChange.unsubscribe();
}

订阅类有一个有趣的特性:

表示一个一次性资源，比如Observable的执行。订阅有一个重要的方法，即unsubscribe，它不接受参数，只处理订阅所持有的资源。 此外，可以通过add()方法将订阅分组在一起，该方法将把一个子订阅附加到当前订阅。当订阅未订阅时，它的所有子(及其孙辈)也将被取消订阅。

您可以创建一个聚合订阅对象，对所有订阅进行分组。 为此，您可以创建一个空的Subscription，并使用它的add()方法向其添加订阅。当组件被销毁时，只需要取消订阅聚合订阅。

@Component({ ... })
export class SmartComponent implements OnInit, OnDestroy {
  private subscriptions = new Subscription();

  constructor(private heroService: HeroService) {
  }

  ngOnInit() {
    this.subscriptions.add(this.heroService.getHeroes().subscribe(heroes => this.heroes = heroes));
    this.subscriptions.add(/* another subscription */);
    this.subscriptions.add(/* and another subscription */);
    this.subscriptions.add(/* and so on */);
  }

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

Angular 2官方文档提供了一个关于何时退订以及何时可以安全忽略的解释。看看这个链接:

https://angular.io/docs/ts/latest/cookbook/component-communication.html !# bidirectional-service

寻找标题为“父母和孩子通过服务通信”的段落，然后是蓝色方框:

注意，当AstronautComponent被销毁时，我们捕获了订阅并取消了订阅。这是一个内存泄漏保护步骤。在这个应用程序中没有实际的风险，因为AstronautComponent的生命周期与应用程序本身的生命周期相同。在更复杂的应用程序中，这并不总是正确的。 我们没有将这个守卫添加到MissionControlComponent中，因为作为父组件，它控制着MissionService的生命周期。

我希望这对你有所帮助。

基于:使用类继承来钩子到Angular 2的组件生命周期

另一种通用方法:

导出抽象类UnsubscribeOnDestroy实现OnDestroy { protected d$: Subject<any>; 构造函数(){ 这一点。d$ = new Subject<void>(); const f = this.ngOnDestroy; 这一点。ngOnDestroy = () => { f (); this.d $ . next (); this.d .complete美元(); }; ｝ public ngOnDestroy() { / /空操作 ｝ ｝

并使用:

@ component ({ 选择器:“my-comp”, 模板:“ }) 导出类RsvpFormSaveComponent扩展UnsubscribeOnDestroy实现OnInit { 构造函数(){ 超级(); ｝ ngOnInit(): void { Observable.of (bla) .takeUntil (this.d $) .subscribe(val => console.log(val)); ｝ ｝

如果需要取消订阅，可以使用以下可观察管道方法的操作符

import { Observable, Subject } from 'rxjs';
import { takeUntil } from 'rxjs/operators';
import { OnDestroy } from '@angular/core';

export const takeUntilDestroyed = (componentInstance: OnDestroy) => <T>(observable: Observable<T>) => {
  const subjectPropertyName = '__takeUntilDestroySubject__';
  const originalOnDestroy = componentInstance.ngOnDestroy;
  const componentSubject = componentInstance[subjectPropertyName] as Subject<any> || new Subject();

  componentInstance.ngOnDestroy = (...args) => {
    originalOnDestroy.apply(componentInstance, args);
    componentSubject.next(true);
    componentSubject.complete();
  };

  return observable.pipe(takeUntil<T>(componentSubject));
};

它可以这样使用:

import { Component, OnDestroy, OnInit } from '@angular/core';
import { Observable } from 'rxjs';

@Component({ template: '<div></div>' })
export class SomeComponent implements OnInit, OnDestroy {

  ngOnInit(): void {
    const observable = Observable.create(observer => {
      observer.next('Hello');
    });

    observable
      .pipe(takeUntilDestroyed(this))
      .subscribe(val => console.log(val));
  }

  ngOnDestroy(): void {
  }
}

操作符包装组件的ngOnDestroy方法。

重点:操作符应该在可观察管道的最后一个。