如何在 Angular2 中取消订阅

Question

如何在 Angular2 中取消订阅？ RxJS 似乎有一个 dispose 方法，但我不知道如何访问它。所以我有可以访问 EventEmitter 并订阅它的代码，如下所示：

var mySubscription = someEventEmitter.subscribe(
    (val) => {
        console.log('Received:', val);
    },
    (err) => {
        console.log('Received error:', err);
    },
    () => {
        console.log('Completed');
    }
);

如何使用mySubscription取消订阅？

Answer 1

您要退订吗？

mySubscription.unsubscribe();

Answer 2

我想我也投入了两分钱。我使用这种模式：

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

@Component({
    selector: 'my-component',
    templateUrl: 'my.component.html'
})
export class MyComponent implements OnInit, OnDestroy {

    private subscriptions: Array<Subscription> = [];

    public ngOnInit(): void {
        this.subscriptions.push(this.someService.change.subscribe(() => {
            [...]
        }));

        this.subscriptions.push(this.someOtherService.select.subscribe(() => {
            [...]
        }));
    }

    public ngOnDestroy(): void {
        this.subscriptions.forEach((subscription: Subscription) => {
            subscription.unsubscribe();
        });
    }
}

编辑

前几天我阅读了文档，发现了一个更推荐的模式：

ReactiveX/RxJS/Subscription

优点：

它在内部管理新订阅并添加了一些简洁的检查。在功能中更喜欢这种方法:)。

缺点：

目前还不是 100% 清楚代码流是什么以及订阅如何受到影响。也不清楚（仅通过查看代码）它如何处理已关闭的订阅以及如果调用 unsubscribe 是否所有订阅都将关闭。

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

@Component({
    selector: 'my-component',
    templateUrl: 'my.component.html'
})
export class MyComponent implements OnInit, OnDestroy {

    private subscription: Subscription = new Subscription();

    public ngOnInit(): void {
        this.subscription.add(this.someService.change.subscribe(() => {
            [...]
        }));

        this.subscription.add(this.someOtherService.select.subscribe(() => {
            [...]
        }));
    }

    public ngOnDestroy(): void {
        /*
         * magic kicks in here: All subscriptions which were added
         * with "subscription.add" are canceled too!
         */
        this.subscription.unsubscribe();
    }
}

Answer 3

编辑：这不适用于 angular2 正在使用的 RxJS 5。

我还以为你正在寻找 Disposable 上的 dispose 方法。

subscribe 方法返回一个 Disposable (link)

我似乎无法在文档中更明确地找到它，但这有效 (jsbin)：

var observable = Rx.Observable.interval(100);

var subscription = observable.subscribe(function(value) {
   console.log(value);
});

setTimeout(function() {
  subscription.dispose();           
}, 1000)

奇怪的是，取消订阅似乎对你有用，而对我却不起作用......

Answer 4

在 Observables for ng2 上取消订阅的解释太多了，我花了很长时间才找到正确的答案。下面是一个工作示例（我试图限制 mousemove）。

import {Injectable, OnDestroy} from "@angular/core";
import {Subscription} from "rxjs";

@Injectable()
export class MyClass implements OnDestroy {
  
  mouseSubscription: Subscription; //Set a variable for your subscription
  
  myFunct() {
    // I'm trying to throttle mousemove
    const eachSecond$ = Observable.timer(0, 1000);
    const mouseMove$ = Observable.fromEvent<MouseEvent>(document, 'mousemove');
    const mouseMoveEachSecond$ = mouseMove$.sample(eachSecond$);
    
    this.mouseSubscription = mouseMoveEachSecond$.subscribe(() => this.doSomethingElse());
  }

  doSomethingElse() {
    console.log("mouse moved");
  }
  
  stopNow() {
    this.mouseSubscription.unsubscribe();
  }
  
  ngOnDestroy() {
    this.mouseSubscription.unsubscribe();
  }
  
}

Answer 5

ngOnDestroy(){
   mySubscription.unsubscribe();
}

最好在销毁组件时取消订阅 rxjs 取消订阅，即从 DOM 中删除以避免不必要的内存泄漏

Answer 6

我个人更喜欢使用 Subject 来关闭组件在销毁生命周期步骤中可能拥有的所有订阅，这可以通过这种方式实现：

import { Component} from '@angular/core';
import { Subject } from "rxjs/Rx";

@Component({
  selector:    'some-class-app',
  templateUrl: './someClass.component.html',
  providers:   []
})

export class SomeClass {  

  private ngUnsubscribe: Subject<void> = new Subject<void>(); //This subject will tell every subscriptions to stop when the component is destroyed.

  //**********
  constructor() {}

  ngOnInit() {

    this.http.post( "SomeUrl.com", {}, null ).map( response => {

      console.log( "Yay." );

    }).takeUntil( this.ngUnsubscribe ).subscribe(); //This is where you tell the subscription to stop whenever the component will be destroyed.
  }

  ngOnDestroy() {

    //This is where we close any active subscription.
    this.ngUnsubscribe.next();
    this.ngUnsubscribe.complete();
  }
}

Answer 7

推荐的方法是使用 RxJS 运算符，例如 takeUntil 运算符。下面是代码 sn-p 显示如何使用它：-

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

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

    constructor() { }

    ngOnInit() {
        var observable1 = interval(1000);
        var observable2 = interval(2000);

        observable1.pipe(takeUntil(this.ngUnsubscribe)).subscribe(x => console.log('observable1: ' + x));
        observable2.pipe(takeUntil(this.ngUnsubscribe)).subscribe(x => console.log('observable2: ' + x));
    }

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

可以找到题目的详细解释here

Answer 8

使用

if(mySubscription){
  mySubscription.unsubscribe();
}

Answer 9

import { Subject } from 'rxjs';
import { takeUntil } from 'rxjs/operators';
import { SomeAPIService } from '../some_file/someAPIService.service.ts

@Component({
  templateUrl: './your_Page.html',
  styleUrls: ['./your_Styles.scss']
})

export class (your class) implements OnInit, OnDestroy {
   // This is a subject variable at it simplest form 
     private unsubscribe$ = new Subject<void>();

     constructor (private someAPIService : SomeAPIService) {}
   
     ngOnit(): void { 
       this.someAPIService.getTODOlist({id:1})
        .pipe(takeUntil(this.unsubscribe$))
         .subscribe((value: SomeVariable) => {
         // What ever value you need is SomeVariable
      },)
    }


     ngOnDestroy(): void {
    // clears all, page subscriptions 
      this.unsubscribe$.next();
      this.unsubscribe$.complete();
     }
`}