Rxjs Distinct operator with key selector in Angular 2 http?

Question

i my angular 2 service i have this method :

  notify(userID: string) {
   return Observable.interval(5000)
      .map(() => this.baseUrl + '/notification/GetUnseen?userId=' + userID)
      .switchMap(url => {
         this.datatService.set(url);
         return this.datatService.get();
    })
     .flatMap(response => response.json().slice())
     .distinct(function (x) { return x.id });
   }

How can i use the distinct operator with key selector in this cas ? When i try to do it i have this error : Property 'id' does not exist on type '{}'.

UPDATE :

The final result i get with this method is :

  {
  id:"f3055770-6e66-4936-8e9a-732b53121549"
  message:"Empty Notification for test ......"
  navigationLink:"/api/home"
  seen:false
  sendedOn:"2016-12-02T15:19:44.856Z"
  userId:null
  }

I would like to filter the result, so if i already have the notification i dont want to get in again

dotcs · Accepted Answer · 2016-12-02 16:26:15Z

2

I don't know exactly how your data structure looks like, but from the example code I guess that you try to map an array to an Observable sequence with this code part:

(...).flatMap(response => response.json().slice())

What you would need to do is create a new Observable sequence with Observable.from and then use switchMap to get it back into the original stream. Then you can use the distinct operator as wished. See this code sample:

const str = JSON.stringify([{id: 1}, {id: 1}, {id: 2}, {id: 1}]);

Rx.Observable.of(str)
  .map(x => JSON.parse(x)) // replication of your sample code until this line
  .switchMap(x => Rx.Observable.from(x))
  .distinct(x => x.id)
  .subscribe(x => console.log(x));

// output:  { id: 1 } 
//          { id: 2 }

Live code on JSBin

answered Dec 2, 2016 at 16:26

dotcs

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3 Comments

Nacim Idjakirene Over a year ago

Can't get your exemple works in my case, maybe i'am missing something

Nacim Idjakirene Over a year ago

when i try this : notify(userID: string) { return Observable.interval(5000) .map(() => this.baseUrl + '/notification/GetUnseen?userId=' + userID) .switchMap(url => { return Observable.from(this.datatService.get(url)); }) .flatMap(response => Observable.from(response.json().slice())) .distinct(x => x.id); } i have only ONE object instead of four !

Waleed Mohsin Over a year ago

it helped me a lot , can you please further explain why we need to create an observable again

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