如何在角度6中将值作为可观察值返回

Question

I want to return value (any data) from service to component as an observable. After a couple of digging into observables found following solution:

class AppService {
    getData(value) {
        // do we have any other best way to return value as an observable
        return Observer.create((observer) => {
            observer.next(value);
        });
    }
}

class AppComponent implements OnInit {
    ngOnInit() {
        this.dataService$ = this.appService.getData().subscribe((data) => {
            // do some task with data
        });
    }
}

Answer 1

Use of like so:

import { of } from 'rxjs';
...
return of(value);

which is equivalent to:

return new Observable(obs => obs.next(value));

However, if you want to convert a given value (eg a Promise, an Observable-like, an Array, an iterable or an array-like object) you may want to use from :

import { from } from 'rxjs';
...
return from(value);

Answer 2

Just return like below

import { Observable, of } from 'rxjs';

...

getData(value) : Observable<any> {
   // Simple way of sending value using of operator.
   return Observable.of(value);
}

Hope this help!

Answer 3

Here's what I do

In your service file :

First I declare my observable this way

  myObs: BehaviorSubject<any> = new BehaviorSubject([]);

In a method you can set your datas into your obs :

var myArray = [1,2,3,4,5];
this.myObs.next(myArray);

If you want your "controller" to subscribe this obs, in your service, just expose a getter :

public getMyObs(){
return this.myObs.asObservable()
}

And in your "controller" you can call it this way :

 ngOnInit() {

this.myService.getMyObs().subscribe(datas => {
    Do What you want with your datas
  }
}