What are possible reasons for an Angular application being unable to retrieve HTTP response data?

Currently diving into the world of Angular services and dependency injection, but encountering a roadblock while attempting to retrieve JSON data from a URL in a service. Here's a snippet of the service.ts code:

import { Injectable } from '@angular/core';
import { HttpClient } from '@angular/common/http';
import { Observable, of } from 'rxjs';
import { Employees } from '../models/emp';

@Injectable()
export class EmployeeService {

  url = 'http://www.mocky.io/v2/5e712acd30000029007a34b8';

  constructor(
    private http: HttpClient
  ) { }

  getEmployees(): Observable<Employees> {
    // make http request to the given url and fetch the contacts
    return this.http.get<Employees>(this.url);
  }

}

Error message displayed in the console:

HttpErrorResponse {headers: {…}, status: 0, statusText: "Unknown Error", url: ""…}

Here is the link to access the StackBlitz demo app:

https://stackblitz.com/edit/angular-osuap2

Answer №1

The main issue you're facing is an inconsistency between your interface and response.

Suppose your API response looks like this:

{
   "empList": [
        {"id": 1, "name": "emp1", "city": "city1"},
        {"id": 2, "name": "emp2", "city": "city2"},
        {"id": 3, "name": "emp3", "city": "city3"},
        {"id": 4, "name": "emp4", "city": "city4"}
    ]    
}

And if you are sending the following request:

getEmployees(): Observable<Employees> {
  // make http request to the given url and fetch the contacts
  return this.http.get<Employees>(this.url);
}

Then your Employees interface should align with the response structure:

export interface Employees {
  empList: Employee[];
}

export interface Employee {
  id: number;
  name: string;
  city: string;
}

Additionally, ensure that your mock API URL is using HTTPS.

Here's a DEMO link for reference: https://stackblitz.com/edit/angular-mr9dz4

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