Typescript convert string to object error

Question

I have a basic problem when i convert the response json from the websocket server to a ts object, but i cannot find where is the error... Can you help to fix it, please?

Here is the websocket server:

const wsServer: Server = new Server({port: WEBSOCKET_PORT});

console.log('WebSocket server is listening on port 8085');
export class PushData {
  constructor(public push: string,
              public workflowId: number) {
  }
}

wsServer.on('connection', (websocket, req) => {
  websocket.send('This message was pushed by WebSocket server');
  websocket.send('Data pushed by server: ');
  websocket.on('message', (message) => {
    console.log('Server received : %s', message);
    const todaysDate = new Date();
    // websocket.send('Data pushed by server: ' + todaysDate.toString());
    const request1 = new PushData('data', 30);
    websocket.send(JSON.stringify(request1));
   }
}

Here is the client Class service:

private faceSubject = new BehaviorSubject<any>(null);
createObservableSocket(url: string): Observable<string> {
  this.ws = new WebSocket(url);
  return new Observable(
    observer => {
      this.ws.onmessage = (event) => observer.next(event.data);
      this.ws.onerror = (event) => observer.error(event);
      this.ws.onclose = (event) => observer.complete();
    }
  );
}

And here is client component where i want to do the convert:

ngAfterViewInit(): void {
  this.drawOverlayPicture();

  // subscribe to the subject
  this.subscription = this.wsService.getFaceSubject()
    .subscribe((data: PushData) => {
        if (data !== null) {
          console.log('received data from server', data);
          console.log('received data from server push=', data.push);
          // var ob = JSON.parse(JSON.stringify(data));
          // console.log('received data from server, workflowId=', (<PushData> ob).push);
          console.log(this.i++);
}

and

export class PushData {
  constructor(public push: string, public workflowId: number) {}
}

Here i got always te data.push = undefined. Can you tell me how to convert the websocket response to object, please?

It's unclear what the problem is. What is console.log('received data from server', data)? — Estus Flask
– Estus Flask, Commented Mar 5, 2018 at 12:37

Mehdi Benmoha · Accepted Answer · 2018-03-05 12:47:56Z

1

EDIT : The server will only push a PushData object when he receives a message from client, but he will send two string to the client on connection. This is why you get data.push is undefined, because data is only strings.

websocket.send('This message was pushed by WebSocket server');  
websocket.send('Data pushed by server: ');

You need to emit a message from the client in order to receive the pushData object !

edited Mar 5, 2018 at 12:47

answered Mar 5, 2018 at 10:58

Mehdi Benmoha

3,9853 gold badges25 silver badges54 bronze badges

Sign up to request clarification or add additional context in comments.

9 Comments

Mehdi Benmoha Over a year ago

Ok thank you, I updated my answer, I thought that this was a special dependency injection syntax. I learned a new thing thank you so much !

pierre Over a year ago

Can you tell me in this case, how to convert the string to object, please? i have tried to use <PushData> data to cast, but it doesn't work.

pierre Over a year ago

For this case, i use: private faceSubject = new BehaviorSubject<PushData>(null); but it doesn't work.

pierre Over a year ago

I tried also to use JSON.parse(data) to create an object, but i got the error: Unexpected token T in JSON at position 0.

Mehdi Benmoha Over a year ago

Read my answer again, you are sending raw strings not PushData object on websocket connection. You need to send an event from the client in order to receive a PushData object, so try in the createObservableSocket sending a message: after the websocket initialization: this.ws.send('Give me a PushData Object plz');

|

Collectives™ on Stack Overflow

Typescript convert string to object error

1 Answer 1

9 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

9 Comments

Your Answer

Sign up or log in

Post as a guest

Related