Angular 2，Observable：http.post，http.get

Question

I have a few problems concerning Http.post and Http.get with Observables. I'm a student and I'm trying to write a simple WebApp and a Server.

I want to post a boolean on my Server if I press a button. The post process does work but everytime I press the button I subscribe another time to the observable. I had the same problem with my http.get method and resolved the problem with this code.

getdata() {   
if(this.subscribtion2 === null){
        this.isValid = false;
      this.subscribtion2 = this.service.get2().subscribe(

         daten => {
            this.jsonobj = daten;
            this.message = 
                [
                this.jsonobj.data.message1,
                ];
            console.log('subscribe')
            ;
            this.myModelneu = this.message[0];     
             },     
         err => this.handleError(err),
         () => console.log('Simple GET completed')
            );

    }else
   {
       this.isValid = true;
       console.log('unsubscribe')
       this.subscribtion2.unsubscribe();
       this.subscribtion2 = null;

   }
}

The get2() method is in a different class.

  get2() {


        return Observable.interval(3000)
          .switchMap(() => this.http.get('http://127.0.0.1:3000/daten/2'))
          .map(res => res.json())

  }

I don't think that is the common way but I can't find another. My http.post look likes this :

post(json: boolean) {
      console.log('post executed');
      console.log(JSON.stringify(json));

     return this.http.post('http://127.0.0.1:3000/login', { json })
     .subscribe();

   } 

I tried to understand the tutorials with Observables but I did not find how to post data on the server without subscribing to the Observable.

Thanks for your help!

Answer 1

The http calls, specifically get and post return an observable that completes with the result, hence you don't need to unsubscribe. On completion the subscription is terminated.