在Angular 2中映射http響應時獲取[object Object]

Question

我在 angular 2 中使用 Observable 地圖時得到一個 [object Object]。

這是來自 API 服務的響應對象。

{
  "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
}

這是我創建的用於映射響應的模型。

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; 
}

調用 http 並映射響應的服務類。

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 || { };
  }

這是調用 Service.ts 的 Component.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);});
}
}

當我看到控制台時，我收到了[object Object]響應。 我無法弄清楚的錯誤在哪里

Answer 1

您的extractData有問題，您希望響應原樣與您的MarketViewModel匹配，因此您需要從該方法中刪除data ，如果沒有響應，還需要返回一個空對象：

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

一些提示：

• 在您的 Service 和 MarketComponent 中，您不需要在構造函數中注入 MarketViewModel。
• 您需要在組件中聲明一個變量marketModel才能使用this.marketModel 。
• 在組件中你已經聲明了方法ngOnInit ，但沒有在你的組件中實現它

在測試您的應用程序時，它有效：

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

您的組件：

marketmodel: MarketViewModel

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

您的觀點，您應該將 html 包裝在 if 語句中，因為您的數據是異步檢索的：

例如：

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

我們需要記住，雖然這段代碼工作得很好，但我們實際上並沒有將響應轉換為您的類的實例。 如果您想這樣做，我建議使用以下鏈接並提供一些很好的答案:) 如何將 JSON 對象轉換為打字稿類

Answer 2

你必須改變你的DashBoardService如下，因為你必須返回MarketListObject數組作為可觀察的而不是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 || [];
  }
}

此外，無需將MarketViewModel作為MarketViewModel中的提供者MarketComponent因此從MarketComponent提供者列表中刪除MarketViewModel MarketComponent如下方式更改您的組件。

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);
    });
  }
}