输入"Promise< string []>"不可分配给'string []'类型 [英] Type 'Promise<string[]>' is not assignable to type 'string[]'

问题描述

出现以下错误: 类型'Promise'不能分配给类型'string []'. 类型"Promise"中缺少属性"includes".

Getting following error: Type 'Promise' is not assignable to type 'string[]'. Property 'includes' is missing in type 'Promise'.

当我将Promise键入"string []"时 我的下面的代码，

when i cast Promise to type 'string[]' My code below,

组件:app.dashboard.ts

import {Component} from '@angular/core';
import { MemberService } from "./app.service";
@Component({
selector:'app-root',
templateUrl:'./app.dashboard.html',
providers:[MemberService]
          })

export class AppDashboard{
  title='Dashboard'
  constructor(private memberService: MemberService) { }

  public doughnutChartLabels:string[] = 
    this.memberService.getmemberheader();//error occurred here
  }
}

Service:app.service.ts

import { Injectable } from '@angular/core';
import { Member } from './Member';
import { Http, Response, Headers, RequestOptions, URLSearchParams } from'@angular/http';
import 'rxjs/add/operator/map';
import 'rxjs/add/operator/toPromise';

@Injectable()
export class MemberService
{
  constructor(private http: Http) {
  }

  private getHeaders(){
    // I included these headers because otherwise FireFox
    // will request text/html instead of application/json
    let headers = new Headers();
    headers.append('Accept', 'application/json');
    return headers;
  }

  getmemberheader(): Promise<string[]> {
    return this.http
        .get(`/ReportService/MemberDatabaseCountryname`, {headers: this.getHeaders()})
        .toPromise()
        .then(this.extractData)
        .catch(this.handleError);
  }  

  private extractData(res: Response) {
    let body = res.json();

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

推荐答案

假定您来自http.get的响应是一个数组，此处您要从函数memberService.getmemberheader返回Promise，则应在其then回调(而不是将诺言本身分配给数组doughnutChartLabels).

Assume your response from http.get is an array, here you are returning Promise from function memberService.getmemberheader, you should retrieve result of promise at its then callback instead (not assigning promise itself to array doughnutChartLabels).

public doughnutChartLabels: string[];

this.memberService.getmemberheader().then(res => {
  this.doughnutChartLabels = res;
})

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