How to create an observable in Angular 2

Question

I am trying to evaluate Angular 2 and I am having problems with observables.

I am trying to create a simple service that initially returns a hard coded array but wil

Answer 1

You can use Observable.of method.

getFleets(): Observable<IFleet[]> {
     return Observable.of(this.fleet)
}

Don't forget to import of using the following line

   import "rxjs/add/observable/of";  // For RxJs  5.0+

For RxJS 6.x

getFleets(): Observable<IFleet[]> {
         return of(this.fleet)
    }

Import statement for "of"

import { of } from "rxjs";

Answer 2

For this you can user BehaviorSubject

export class FleetListService {
    public data: any = new BehaviorSubject('your hard coded data goes here');
    getdata() {
        //do your stuff
        this.FleetListService.next('new data got from server');
    }
}

One of the variants of Subjects is the BehaviorSubject, which has a notion of "the current value". It stores the latest value emitted to its consumers, and whenever a new Observer subscribes, it will immediately receive the "current value" from the BehaviorSubject. Behaviour subject always returns last data. For more info

Answer 3

This is coming a bit late, just for clarification anyways. This is how you can create a simple observable in case you want to mimic your own like promise. You do

let observable=Observable.create(observer => {
      setTimeout(() => {
        observer.next("data to send can be object or anything");
        console.log("am done");
        observer.complete(); // to show we are done with our processing
       // observer.error(new Error("error message"));
      }, 2000);

    })

to subscribe to it is very easy

observable.subscribe((data) => {
console.log(data); // should be 'data to send can be object or anything'
});

you can also convert it to promise using toPromise() or fromPromise(observable) operator and so on.