typescript 类型 Promise<void> 不可分配给类型 Promise<customType[]>
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Type Promise<void> is not assignable to type Promise<customType[]>
提问by MARKAND Bhatt
I am new to angularJs2. I have created following service:
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);
}
}
Following are my Typescript compile configuration of Vs2017
以下是我对 Vs2017 的 Typescript 编译配置
When I compile the code using visual studio 2017 I get following error
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[]>'.**
**TS2322 Build:Type 'Promise<void>' is not assignable to type 'Promise<customType[]>'.**
Help me to fix this error.
帮我修复这个错误。
回答by Saravana
You are not returning anything inside your thenwhich makes jobsbe of type Promise<void>. Return the array inside then:
你是不是给您回里的任何东西then，这使得jobs具有类型Promise<void>。返回里面的数组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
查看 promise 的链接行为：https: //developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise/then#Chaining
回答by Stephen R. Smith
I've added the 'catch' operator, and swapped your interface import for an interface definition in the code (as I don't obviously have access to yours). I can't really test this without the rest of your project code, but it looks right to me and doesn't throw any errors in VSC.
我添加了“catch”运算符，并将您的接口导入替换为代码中的接口定义（因为我显然无法访问您的）。如果没有您的项目代码的其余部分，我无法真正测试它，但它在我看来是正确的，并且不会在 VSC 中引发任何错误。
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);
}
}
