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

问题

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.

回答1:

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.

来源：https://stackoverflow.com/questions/44202862/angular2-error-while-resolving-promise-type-promisehero-is-no-t-assignabl