javascript - 类型 Promise 不可分配给类型 Promise

Question

我是 angularJs2 的新手。我创建了以下服务:

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);
    }
}

以下是我的 Vs2017 的 Typescript 编译配置



当我使用 Visual Studio 2017 编译代码时，出现以下错误
**TS2322 Build:Type 'Promise<void>' is not assignable to type 'Promise<customType[]>'.* *

帮我解决这个错误。

Answer 1

您没有返回您的 then 中的任何内容这使得 jobs属于 Promise<void> 类型.返回 then 内的数组:

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;
}

查看 Promise 的链接行为: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise/then#Chaining