I am having a service that has this method:
export class TestModelService {
public testModel: TestModel;
constructor( @Inject(Http) public http: Http) {
}
public fetchModel(uuid: string = undefined): Observable<string> {
if(!uuid) {
//return Observable of JSON.stringify(new TestModel());
}
else {
return this.http.get("http://localhost:8080/myapp/api/model/" + uuid)
.map(res => res.text());
}
}
}
in the component's constructor I am subscribing like this:
export class MyComponent {
testModel: TestModel;
testModelService: TestModelService;
constructor(@Inject(TestModelService) testModelService) {
this.testModelService = testModelService;
testService.fetchModel("29f4fddc-155a-4f26-9db6-5a431ecd5d44").subscribe(
data => { this.testModel = FactModel.fromJson(JSON.parse(data)); },
err => console.log(err)
);
}
}
This works if an object comes from the server but I am trying to create an observable that will work with the given subscribe()
call for a static string (this happens when testModelService.fetchModel()
does not receive an uuid) so there is seamless handling in both cases.
This question is related to
typescript
promise
angular
observable
rxjs
As of July 2018 and the release of RxJS 6
, the new way to get an Observable from a value is to import the of
operator like so:
import { of } from 'rxjs';
and then create the observable from the value, like so:
of(someValue);
Note, that you used to have to do Observable.of(someValue)
like in the currently accepted answer. There is a good article on the other RxJS 6 changes here.
This is how you can create a simple observable for static data.
let observable = Observable.create(observer => {
setTimeout(() => {
let users = [
{username:"balwant.padwal",city:"pune"},
{username:"test",city:"mumbai"}]
observer.next(users); // This method same as resolve() method from Angular 1
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); // users array display
});
I hope this answer is helpful. We can use HTTP call instead static data.
Things seem to have changed since Angular 2.0.0
import { Observable } from 'rxjs/Observable';
import { Subscriber } from 'rxjs/Subscriber';
// ...
public fetchModel(uuid: string = undefined): Observable<string> {
if(!uuid) {
return new Observable<TestModel>((subscriber: Subscriber<TestModel>) => subscriber.next(new TestModel())).map(o => JSON.stringify(o));
}
else {
return this.http.get("http://localhost:8080/myapp/api/model/" + uuid)
.map(res => res.text());
}
}
The .next()
function will be called on your subscriber.
This way you can create Observable from data, in my case I need to maintain shopping cart:
service.ts
export class OrderService {
cartItems: BehaviorSubject<Array<any>> = new BehaviorSubject([]);
cartItems$ = this.cartItems.asObservable();
// I need to maintain cart, so add items in cart
addCartData(data) {
const currentValue = this.cartItems.value; // get current items in cart
const updatedValue = [...currentValue, data]; // push new item in cart
if(updatedValue.length) {
this.cartItems.next(updatedValue); // notify to all subscribers
}
}
}
Component.ts
export class CartViewComponent implements OnInit {
cartProductList: any = [];
constructor(
private order: OrderService
) { }
ngOnInit() {
this.order.cartItems$.subscribe(items => {
this.cartProductList = items;
});
}
}
Source: Stackoverflow.com