Angular 4 Error : Property 'includes' is missing in type '() => any'

Question

I am getting error while using angular 4 and observable.

/Users//backend/src/app/app.component.ts (15,55): Type '() => any' is not assignable to type 'State[]'. /Users//backend/src/app/app.component.ts (15,55): Type '() => any' is not assignable to type 'State[]'. Property 'includes' is missing in type '() => any'.

What am I doing wrong

My Model

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

My Service

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));
  }
}

My Component

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 { }

Answer 1

There are two issues.

First, you aren't invoking a json response, you are simply referencing the method. You need to change res.json to res.json():

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

Second, you aren't declaring a type for the result of your subscribe. You should explicitly specify the type of the result:

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

Since the parameter from your subscribe is of type any, unless you specify a type up front as I have above, or cast it before assignment, the typescript compiler will let you know that the types are invalid.

Answer 2

In my case res.json() was not an available function. Also another difference: My http service returns the whole 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);
  }
}

... then I read the output of the Observable from my AppComponent:

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