在Angular 2中映射http响应时获取[object Object]

Question

I am getting an [object Object] while using Observable map in angular 2.

Here is the response object from the API service.

{
  "isSuccess": true,
  "message": "Connection Successfull",
  "data": [
    {
      "marketId": 1,
      "city": "san",
      "cityF": "san",
      "name": null,
      "nameF": "hello",
      "sortOrder": 1,
      "isActive": true
    },
    {
      "marketId": 2,
      "city": "san",
      "cityF": "san",
      "name": null,
      "nameF": "hello",
      "sortOrder": 1,
      "isActive": true
    },
    {
      "marketId": 3,
      "city": "san",
      "cityF": "san",
      "name": null,
      "nameF": "hello",
      "sortOrder": 1,
      "isActive": true
    },
    {
      "marketId": 4,
      "city": "san",
      "cityF": "san",
      "name": null,
      "nameF": "hello",
      "sortOrder": 1,
      "isActive": true
    }
  ],
  "exceptionErrorMessage": null,
  "errorCode": 0,
  "successMessage": null
}

Here is the model I have created to map with the response.

export class MarketViewModel 
{
public isSuccess: boolean;
public message : string;
public successMessage : string;
public exceptionErrorMessage : string;
public errorCode: number;
public data: MarketListObject[];

}
export class MarketListObject 
{
    public marketId : number;
    public city: string;
    public cityF : string;
    public name : string;
    public nameF : string;
    public sortOrder : number;
    public isActive : boolean; 
}

Service class to call the http and map the response.

import { Headers, RequestOptions } from '@angular/http';
import { Router, ActivatedRoute, Params } from '@angular/router';
import { MarketViewModel} from "../ViewModel/Market.ViewModel";
import { Injectable }     from '@angular/core';
import { Http, Response } from '@angular/http';
import {Observable} from 'rxjs/Rx';
import 'rxjs/add/operator/map';
import 'rxjs/add/operator/catch';

@Injectable()
export class DashBoardService {
    private MarketUrl = "DashBoard/GetMarketList";
    private ResponseData: any;
    constructor(private http: Http, private router: Router, private  marketModel : MarketViewModel) {}

    public GetMarketListCall() :Observable<MarketViewModel> {
         return this.http.get(this.MarketUrl).map(this.extractData)
                    .catch(this.handleError);
    } 
private extractData(res: Response) {
    let body = res.json();
        console.log("Body Data = "+body.data);
    return body.data || { };
  }

Here is the Component.ts which is calling Service.ts

import { Component } from '@angular/core';
import { MarketViewModel} from "../ViewModel/Market.ViewModel";
import { DashBoardService} from "../Service/DashBoard.Service";
import { Observable } from 'rxjs/Observable';

 @Component({
     selector: 'Market-app',
    templateUrl: 'DashBoard/MarketListView',
    providers: [DashBoardService, MarketViewModel]
 })

export class MarketComponent {
  constructor(private DashBoardservice: DashBoardService, private  marketModel : MarketViewModel) {
   }

ngOnInit() {
        this.DashBoardservice.GetMarketListCall().subscribe(
                               data => {this.marketModel = data;
                                    console.log("this"+this.marketModel); }, 
                                err => {console.log(err);});
}
}

When I see to the console I am getting [object Object] response. Where is the mistake I am not able to figure it out

Answer 1

You have a problem with your extractData , you want the response as it is, to match your MarketViewModel , so you need to remove the data from that method and also to return an empty object if there is no response:

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

Some pointers:

• In your Service and MarketComponent you do not need to inject the MarketViewModel in your constructor.
• You need to declare a variable marketModel in your component, to be able to use this.marketModel .
• In component you have declared method ngOnInit , but not implemented it in your component

When testing your app it worked:

getMarketListCall(): Observable<MarketViewModel>{
    return this.http.get('theUrl')
        .map(res => res.json()) // or use the 'extractData'
        // .catch(this.handleError);
}

Your component:

marketmodel: MarketViewModel

ngOnInit() {
    this.DashBoarservice.GetMarketListCall()
       .subscribe(data => {
          this.marketModel = data;
        },
        err => { console.log(err); 
    });
}

Your view, you should wrap your html in an if-statement, since your data gets retrieved asynchronously:

eg:

<div *ngIf="marketModel"> <!-- Here! -->
  <h2>MarketModel Message: {{marketModel.message}}</h2>
  <div *ngFor="let data of marketModel.data">Id: {{data.marketId}} </div>
</div><br>

We need to remember though this code works wonderfully, we have not actually casted the response to be of instances of your classes. If you wish to do that, I suggest the following link with some great answers :) How do I cast a JSON object to a typescript class

Answer 2

You have to change your DashBoardService as below as you are have to return MarketListObject array as observable not MarketViewModel :

@Injectable()
export class DashBoardService {
  private MarketUrl = "DashBoard/GetMarketList";
  private ResponseData: any;

  constructor(private http: Http, private router: Router, private  marketModel : MarketViewModel) {}

  public GetMarketListCall() :Observable<MarketListObject[]> {
     return this.http.get(this.MarketUrl).map(this.extractData)
                .catch(this.handleError);
  } 

  private extractData(res: Response) {
    let body = res.json();
    console.log("Body Data = "+body.data);
    return body.data || [];
  }
}

Also there is no need to pass MarketViewModel as providers inside MarketComponent so remove MarketViewModel from MarketComponent providers list and change your component as below .

import { Component } from '@angular/core';
import { DashBoardService} from "../Service/DashBoard.Service";
import { Observable } from 'rxjs/Observable';

@Component({
  selector: 'Market-app',
  templateUrl: 'DashBoard/MarketListView',
  providers: [DashBoardService]
})
export class MarketComponent {

  public marketList: any[];

  constructor(private dashBoardservice: DashBoardService) {
  }

  ngOnInit() {
    this.dashBoardservice.GetMarketListCall().subscribe((data) => { 
      this.marketList = data;
      console.log("this" + this.marketList);
    },(err) => {
      console.log(err);
    });
  }
}