/blog/posts/20170127-Angular2TutorialWithAsyncAndAwait.html

[damirarh]

Imported

URL: https://www.damirscorner.com/blog/posts/20170127-Angular2TutorialWithAsyncAndAwait.html

[damirarh]

Imported comment written by Emiliano on 2017-08-04T15:10:58

How did you implement the toPromise() method?
Do you have the source code?
Thanks

[damirarh]

Imported comment written by +380 on 2017-08-04T16:34:22

Add to main.ts:
import 'rxjs/add/operator/toPromise';

[damirarh]

Imported comment written by Damir Arh on 2017-08-04T17:44:53

Observable.toPromise() is a part of RxJS. To use it, you only need to add the following import at the top of the source file:

import 'rxjs/add/operator/toPromise';

[damirarh]

Imported comment written by Ken Perregaux on 2017-09-12T20:18:36

What happens if you service throws an error? What does the client do?
e.g. You want to display an error to the user.

[damirarh]

Imported comment written by Damir Arh on 2017-09-13T12:49:59

In case of an error, service methods still reject the returned promises, as they did before my changes to the code.

When using async/await in component methods as well, you can catch the errors with a try/catch block as I did in the changed getHeroes method, for example:

try {
  let heroes = await this.heroService.getHeroesSlowly();
  this.heroes = heroes;
} catch (error) {
  /* handle error */
}

[damirarh]

Imported comment written by Ryan Buening on 2017-11-21T03:48:50

@damirarh:disqus I'm trying something similar to what you have, but TypeScript 2.6.1 is throwing a compile error. I created a StackOverflow question here: https://stackoverflow.com/q.... Any ideas?

[damirarh]

Imported comment written by Damir Arh on 2017-11-21T07:21:38

It seems Typescript 2.6.1 is more strict regarding return type checking. Check Aaron's answer for the options that are available to you. I might update the blog post after I take a closer look at it myself.

[damirarh]

Imported comment written by Ryan Buening on 2017-11-21T12:15:23

Thanks for the reply. I'll look into Aaron's answer.

[damirarh]

Imported comment written by Damir Arh on 2017-12-26T09:45:31

Since I've written the blogpost, the Tour of Heroes tutorial has been rewritten to a great extent. HeroService functions don't even return promises any more, making the conversion to async/await as described above impossible and useless. In light of that, keeping the blogpost unchanged makes much more sense. Fortunately I included original function implementations in the post, preserving most of its educational value.