類型Promise <void>不可分配類型Promise <customType []>

Question

我是angularJs2的新手。我創建了以下服務：

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); 
    } 
} 

以下是我的打字稿編譯Vs2017

的配置當我使用的Visual Studio 2017年我獲得以下錯誤

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

編譯代碼

幫我解決這個錯誤。

Answer 1

不必返回你then這使得jobs是Promise<void>類型的內部事情。返回數組裏面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; 
} 

見承諾的鏈接行爲：https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise/then#Chaining

Answer 2

我已經添加了'catch'運算符，並將代碼中的接口定義的接口導入交換（因爲我顯然沒有訪問您的接口）。如果沒有剩下的項目代碼，我無法真正測試它，但它看起來很適合我，並且不會在VSC中引發任何錯誤。

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

import 'rxjs/add/operator/toPromise'; 
import 'rxjs/add/operator/catch'; 


export interface customType{ 
} 


@Injectable() 
export class JobService implements OnInit { 

    constructor(private http: Http) { } 
    private jobs: Promise<customType[]>; 

    ngOnInit(): void { 
     this.jobs = 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[]> { 
     return this.http.get(this.ordersUrl) 
      .map(response => response.json()) 
      .catch(this.handleError) 
      .toPromise(); 

    } 

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