Question

我想在取消订阅可观察对象时删除事件侦听器。我的问题是如何检查是否删除了事件监听器。有什么方法可以检查事件监听器是否已删除？

DB_CONNECTION=mysql
DB_HOST=127.0.0.1
DB_PORT=3306
DB_DATABASE=bank
DB_USERNAME=root
DB_PASSWORD=

还有我的组件：

export class BroadcastService {

  public events: Observable < any > ;
  public channel = new BroadcastChannel('test_channel');

  constructor() {
    this.events = Observable.create((observer) => {

      const listener = (ev) => {
        observer.next(ev.data),
          console.log("on")
      };
      this.channel.addEventListener('message', listener);

      return () => {
        this.channel.removeEventListener('message', listener);
      };
    });
  }

  public addPerson(person: any) {
    this.channel.postMessage(person);
  }

}

Answer 1

您可以在服务中手动执行此操作：

import { Observable } from 'rxjs';

export class BroadcastService {

  public events: Observable<any>;
  public channel = new BroadcastChannel('test_channel');

  constructor() {
    this.events = Observable.create((observer) => {

      this.channel.addEventListener('message', (ev) => {
        observer.next(ev.data)
      });

      return () => {
        this.channel.removeEventListener('message', (ev) => {
          observer.next({
            ...ev.data,
            removed: true
          })
        });
      };
    });
  }

  public addPerson(person: any) {
    this.channel.postMessage(person);
  }

}

订阅后，您可以检查数据是否具有removed属性。

如何检查eventListener是否已删除？

1 个答案: