Angular2 Observable and Promise

Question

I started using Angular2 Observable, but I can\'t find something similar to .then that I used with Promises.

This is what I want

Answer 1

When you call subscribe(...) a Subscription is returned which doesn't have a toPromise(). If you move the code from subscribe to map you can use toPromise() instead of subscribe

return this._httpClient.post('LoginAction', credentials)
  .map(res => res.json())
  .map(user => {
    return new User(user);
  }).toPromise();

and the caller will get a Promise where he can get the value using

public login() {
    this._user = AuthService.getInstance().login(this._loginInfo)
    .then(result => {
      doSomething();
    });
}

but you get the same result if you omit `.toPromise() and the caller uses it like

public login() {
    this._user = AuthService.getInstance().login(this._loginInfo)
    .subscribe(result => {
      doSomething();
    });
}

where the only difference is subscribe() instead of then() and if the user of the library prefers the reactive style he will prefer using subscribe() like he is used to.