Angular2 Error while resolving Promise: Type 'Promise<Hero[]>' is no t assignable to type 'Hero[]'

Question

Updated.

I am Following Angular2 tutorial from https://angular.io/docs/ts/latest/tutorial/toh-pt4.html

Here is the call to HeroService from heroes.component.ts,

Heroes.component.ts

import { Component , OnInit } from '@angular/core';

import { Hero } from './hero';

import { HeroService } from './hero.service';



@Component({
  selector: 'my-heroes',
  template: `


        <h2>My Heroes</h2>
        <ul class="heroes">
            <li *ngFor="let hero of heroes">
                 <span class="badge">{{hero.id}}</span> {{hero.name}}
            </li>
         </ul> `,

})

export class HeroesComponent implements OnInit {
    title = 'Tour of Heroes';
    heroes: Hero[];
    selectedHero: Hero;

    constructor(private heroService : HeroService ){

    }

    getHeroes(): void{
      this.heroService.getHeroes().then(heroes => this.heroes = heroes);
    }

    ngOnInit(): void{
        this.getHeroes();
    }


}

And getHeroes() call written in HeroService

HeroService.ts

import { Injectable } from '@angular/core';
import { Hero } from './hero';
import { HEROES } from './mock-heroes';

@Injectable()
export class HeroService{
    getHeroes() { 
       return Promise.resolve(HEROES);
     }
}

I get the following compile time error :

error TS2322: Type 'Promise' is not assignable to type 'Hero[]'. Property 'length' is missing in type 'Promise'.

Please suggest.

Can you show the full Component code for where you have those 2 functions please? You can exclude anything that is not mentioned in those code blocks of your — borislemke
at that page of the tutorial, you should import in the hero service the mock-heroes. Did you import it correctly? import { HEROES } from './mock-heroes'; And of course defining the file moch-heroes witht he list of heroes — quirimmo
Can you provide the full Error line? It should mention a file and line number. I have a suspicion, but the line number will make sure. Tell us which line in your question the line number refers to in the error — borislemke
I had a similar error in the tutorial. Restarting the server fixed my problem. See stackoverflow.com/questions/44216533/… — rodrunner

Olivier Cadoz Olivier Cadoz · Accepted Answer · 2017-08-28T10:47:16

Changing heroes: Hero[]; to heroes: any; resolves the issue, however the console returns an error because ngFor supports only iterables. At the end, the code compile and the app runs but there's this tiny issue that I find disrupting.

Angular2 Error while resolving Promise: Type 'Promise<Hero[]>' is no t assignable to type 'Hero[]'

1 Answers