Angular2/Websocket:如何为传入的Websocket消息返回可观察值 [英] Angular2/Websocket: how to return an observable for incoming websocket messages

问题描述

我将使用Angular2接收websocket传入的消息，并根据收到的消息更新网页.现在，我正在使用虚拟echo websocket服务，并将其替换.

I'm going to use Angular2 to receive websocket incoming messages and update a webpage based on those received messages. Right now, I'm using a dummy echo websocket service and will replace it.

据我所知，接收websocket消息的函数必须返回一个Observable，该Observable由将更新网页的处理程序订阅.但是我不知道如何返回一个可观察值.

From my understanding, the function which receive websocket messages has to return an observable that is subscribed by a handler who will update the webpage. But I can't figure out how to return an observable.

代码段附在下面. MonitorService创建一个websocket连接，并返回一个包含所接收消息的可观察对象.

Code snippet is attached below. The MonitorService creates a websocket connection and return an observable containing the received messages.

@Injectable()
export class MonitorService {

    private actionUrl: string;
    private headers: Headers;
    private websocket: any;
    private receivedMsg: any;
    constructor(private http: Http, private configuration: AppConfiguration) {

        this.actionUrl = configuration.BaseUrl + 'monitor/';
        this.headers = new Headers();
        this.headers.append('Content-Type', 'application/json');
        this.headers.append('Accept', 'application/json');
    }

    public GetInstanceStatus = (): Observable<Response> => {
        this.websocket = new WebSocket("ws://echo.websocket.org/"); //dummy echo websocket service
        this.websocket.onopen =  (evt) => {
            this.websocket.send("Hello World");
        };

        this.websocket.onmessage = (evt) => { 
            this.receivedMsg = evt;
        };

        return new Observable(this.receivedMsg).share();
    }

}

下面是另一个组件，该组件订阅从上面返回的可观察对象并相应地更新网页.

Below is another component which subscribes to the observable returned from above and updates webpages correspondingly.

export class InstanceListComponent {
  private instanceStatus: boolean
  private instanceName: string
  private instanceIcon: string
  constructor(private monitor: MonitorService) { 
    this.monitor.GetInstanceStatus().subscribe((result) => {
        this.setInstanceProperties(result);
    });
  }

  setInstanceProperties(res:any) {
    this.instanceName = res.Instance.toUpperCase();
    this.instanceStatus = res.Status;
    if (res.Status == true)
    {
      this.instanceIcon = "images/icon/healthy.svg#Layer_1";
    } else {
      this.instanceIcon = "images/icon/cancel.svg#cancel";
    }
  }
}

现在，我在浏览器控制台中遇到此错误 TypeError: this._subscribe is not a function

Now, I'm running into this error in the browser console TypeError: this._subscribe is not a function

推荐答案

我将其放在

I put it on a plunker and I added a function for sending message to the Websocket endpoint. Here is the important edit:

public GetInstanceStatus(): Observable<any>{
    this.websocket = new WebSocket("ws://echo.websocket.org/"); //dummy echo websocket service
    this.websocket.onopen =  (evt) => {
        this.websocket.send("Hello World");
    };
    return Observable.create(observer=>{
        this.websocket.onmessage = (evt) => { 
            observer.next(evt);
        };
    })
    .share();
}

更新
正如您在评论中提到的，更好的替代方法是使用Observable.fromEvent()

Update
As you mentioned in your comment, a better alternative way is to use Observable.fromEvent()

websocket = new WebSocket("ws://echo.websocket.org/");
public GetInstanceStatus(): Observable<Event>{
    return Observable.fromEvent(this.websocket,'message');
}

Observable.fromEvent()的

插件示例 ;

此外，您也可以使用WebSocketSubject进行操作，尽管它似乎还没有准备好(从rc.4开始):

Also, you can do it using WebSocketSubject, although, it doesn't look like it's ready yet (as of rc.4):

constructor(){
  this.websocket = WebSocketSubject.create("ws://echo.websocket.org/");
}

public sendMessage(text:string){
  let msg = {msg:text};
  this.websocket.next(JSON.stringify(msg));
} 

插件示例

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