Type Promise<void> is not assignable to type Promise<customType[]>

Question

I am new to angularJs2. I have created following service:

import { Injectable, OnInit } from '@angular/core';
import { customType } from '../models/currentJobs';
import { Headers, Http } from '@angular/http';

import 'rxjs/add/operator/toPromise';

@Injectable()
export class JobService implements OnInit {

    constructor(private http: Http) { }

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

    private headers: Headers = new Headers({ 'Content-Type': 'application/json' });
    private ordersUrl: string = 'http://localhost:35032/api/order/';

    public orders: customType[];

    getCurrentJobs(): Promise<customType[]> {
        var jobs =  this.http.get(this.ordersUrl)
            .toPromise()
            .then(response => {
                this.orders = response.json() as customType[];
            })
            .catch(this.handleError);
        return jobs;//this line throws error
    }

    private handleError(error: any): Promise<any> {
        console.error('An error occurred', error);
        return Promise.reject(error.message || error);
    }
}

Following are my Typescript compile configuration of Vs2017

When I compile the code using visual studio 2017 I get following error

**TS2322 Build:Type 'Promise<void>' is not assignable to type 'Promise<customType[]>'.**

Help me to fix this error.

Answer 1

You are not returning anything inside your then which makes jobs be of type Promise<void>. Return the array inside then:

getCurrentJobs(): Promise<customType[]> {
    var jobs = this.http.get(this.ordersUrl)
      .toPromise()
      .then(response => {
        this.orders = response.json() as customType[];
        return this.orders;
      })
      .catch(this.handleError);
    return jobs;
}

See the chaining behaviour of promises: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise/then#Chaining