如何从JSON对象获取数据到Angular？

Question

For the array list case (with bracket) everything works fine

This work properly for me:

export interface IPage {
  size: number;
pageSize: number;
numberOfPage: number;
object: ICompany[];
}

export interface ICompany {
name: string;
country: string;
taxID: string;
numberOfAds: number;
}

[{
  "size": 10,
  "pageSize": 20,
  "numberOfPage": 1,
  "object": [
    {
      "name": "Pirates Limited",
      "country": "Poland",
      "taxID": "e",
      "numberOfAds": 1
    },
    {
      "name": "Test company",
      "country": "Poland",
      "taxID": "fads",
      "numberOfAds": 2
    }
}]

import { Injectable } from '@angular/core';
import { HttpClient, HttpErrorResponse } from '@angular/common/http';
import { IPage} from './page';
import { Observable } from 'rxjs';

@Injectable()
export class CompanyService {

//private _url: string = "http://localhost:4200/api/company?page=1";
private _url: string = "/assets/data/page.json";


  constructor(private http:HttpClient) { }

getCompany(): Observable<IPage>{
    return this.http.get<IPage>(this._url);
  }
  errorHandler(error: HttpErrorResponse){
    return Observable.throw(error.message || "Server Error");
}


}

index.componenet.ts 
this._companyService.getCompany()
.subscribe(data => this.company = data,
                 error => this.errorMsg = error);

index.componenet.html

 <ul *ngFor="let c of company">
      <li>{{c.size}}, {{c.pageSize}}</li>
    </ul>

but when i change to json object (without []):

{
  "size": 10,
  "pageSize": 20,
  "numberOfPage": 1,
  "object": [
    {
      "name": "Pirates Limited",
      "country": "Poland",
      "taxID": "e",
      "numberOfAds": 1
    },
    {
      "name": "Test company",
      "country": "Poland",
      "taxID": "fads",
      "numberOfAds": 2
    }
}

It does not work good for me. What i need to do when I do not use JSON array? What change should I make if I do not use the list. This code for the key value does not work for me.

Answer 1

You can add logic to check result is array or not, if not convert it to array.

this._companyService.getCompany()
.subscribe(data => {
    if(!Array.isArray(obj)){
    this.company = [data]
    }else{
     this.company = data;
    }
},
error => this.errorMsg = error);

Answer 2

Map the result woth RxJS operators :

return this.http.get<IPage>(this._url).pipe(map(a => a[0]));

This will return the first element of the array.