Angular 4 错误：“() => any”类型中缺少属性“includes”答案

【问题标题】：Angular 4 Error : Property 'includes' is missing in type '() => any'Angular 4 错误：“() => any”类型中缺少属性“includes”
【发布时间】：2017-09-14 23:33:53
【问题描述】：

我在使用 angular 4 和 observable 时遇到错误。

/Users//backend/src/app/app.component.ts (15,55)：类型 '() => any' 不可分配给类型 'State[]'。 /Users//backend/src/app/app.component.ts (15,55)：类型 '() => any' 不可分配给类型 'State[]'。类型“() => any”中缺少属性“includes”。

我做错了什么

我的模特

export class State {
  id: number;
  state: string;
  code: string;
}

我的服务

import { Injectable } from '@angular/core';
import { Http, Response } from '@angular/http';
import 'rxjs/add/operator/map';
import 'rxjs/add/operator/do';
import 'rxjs/add/operator/toPromise';

import {environment} from '../../../environments/environment';

@Injectable()

export class StateService {
  private baseUrl: string = environment.baseUrl;

  constructor( private http: Http) {}

  /**
   * Get all States
   */
  GetStates() {
   return this.http.get(this.baseUrl + 'v1/states')
      .map((res: Response) => res.json);
     // .do( data => console.log(data));
  }
}

我的组件

import { Component, OnInit } from '@angular/core';
import {StateService} from './shared/services/state.service';
import {State} from './shared/models/state';

@Component({
  selector: 'app-root',
  templateUrl: './app.component.html',
  styles: []
})
export class AppComponent implements OnInit {
   states: State[] ;
  constructor(private stateService: StateService) {}

  ngOnInit() {
    this.stateService.GetStates().subscribe(states => this.states = states );
  }
}

App.Module

import { BrowserModule } from '@angular/platform-browser';
import { NgModule } from '@angular/core';
import { FormsModule } from '@angular/forms';
import { HttpModule } from '@angular/http';
import 'rxjs/add/operator/map';

import { AppRoutingModule } from './app-routing.module';
import { AppComponent } from './app.component';
import { StateService } from './shared/services/state.service';
@NgModule({
  declarations: [
    AppComponent
  ],
  imports: [
    BrowserModule,
    FormsModule,
    HttpModule,
    AppRoutingModule
  ],
  providers: [
    StateService
  ],
  bootstrap: [AppComponent]
})
export class AppModule { }

【问题讨论】：

标签： angular typescript

【解决方案1】：

有两个问题。

首先，您不是在调用 json 响应，您只是在引用该方法。你需要把res.json改成res.json()：

.map((res: Response) => res.json());

其次，您没有为订阅结果声明类型。您应该明确指定结果的类型：

this.stateService.GetStates().subscribe((states: State[]) => this.states = states);

由于您订阅的参数是any 类型，除非您像我上面提到的那样预先指定类型，或者在赋值之前对其进行强制转换，否则打字稿编译器会告诉您类型无效。

【讨论】：

这适用于 Angular 6：this.stateService.GetStates().subscribe((states: State[]) => this.states = states);

【解决方案2】：

在我的例子中 res.json() 不是一个可用的函数。还有另一个区别：我的 http 服务返回整个 Observable...

import { Injectable, OnInit } from '@angular/core';
import { HttpClient, HttpErrorResponse } from "@angular/common/http";
import { Dashboard } from "./app.component";
import { HttpHeaders } from "@angular/common/http";
import { Observable } from "rxjs/Observable";
import 'rxjs/add/operator/catch';
import 'rxjs/add/operator/map';



@Injectable()
export class HttpServiceService {

  public dashboards;

  constructor(private http: HttpClient) {}

  public handleError(error: any): Promise<any> {
    console.error('An error occurred', error); // for demo purposes only
    return Promise.reject(error.message || error);
  }


  getDashboard() : any {

    let results;
    const headers = new HttpHeaders()
      .set('Access-Control-Allow-Origin','*')
      .set('Content-Type', 'application/json');

    return this.http.get('http://localhost:8080/dashboards',
      {headers,responseType: "json"}).catch(this.handleError);
  }
}

...然后我从我的 AppComponent 中读取 Observable 的输出：

constructor(private http:HttpServiceService) {    
  this.http.getDashboard().subscribe(results => this.dashboardList = results);
}

【讨论】：