Angular - Get Error: Error trying to diff '[object Object]'. Only arrays and iterables are allowed

Question

I am now building my front-end now on Angular and for the life of me, I cannot see what is causing this error. I am using Node.js as my backend. Below is my code.

country.ts

export class Country {
  id?: string;
  name?: string;
  icon?: string;
  imageFlag?: string;
}

countries.services.ts

export class CountriesService {
  constructor(private http: HttpClient) {}

  getCountries(): Observable<Country[]> {
    return this.http.get<Country[]>('http://127.0.0.1:3300/api/v1/countries/');
  }
}

countries-list.component.ts

export class CountriesListComponent implements OnInit {
  countries: Country[] = [];

  constructor(private countriesService: CountriesService) {}

  ngOnInit(): void {
    this.countriesService.getCountries().subscribe((amazwe) => {
      this.countries = amazwe;
      console.log(amazwe);
    });
  }
}

My console on console.log(amazwe) depicts the below

{
    "status": "success",
    "results": 7,
    "data": {
        "data": [
            {
                "_id": "61c4827a69a96679469adac2",
                "name": "Botswana",
                "icon": "Safari iCON",
                "imageFlag": "Botswana Flag",
                "__v": 0,
                "id": "61c4827a69a96679469adac2"
            },
            {
                "_id": "61c482ab69a96679469adac4",
                "name": "South Africa",
                "icon": "Safari iCON",
                "imageFlag": "South Africa Flag",
                "__v": 0,
                "id": "61c482ab69a96679469adac4"
            },
            {
                "_id": "61c482c369a96679469adac6",
                "name": "Namibia",
                "icon": "Safari iCON",
                "imageFlag": "Namibia Flag",
                "__v": 0,
                "id": "61c482c369a96679469adac6"
            },
            {
                "_id": "61c482f569a96679469adac8",
                "name": "Mozambique",
                "icon": "Safari iCON",
                "imageFlag": "Mozambique Flag",
                "__v": 0,
                "id": "61c482f569a96679469adac8"
            },
            {
                "_id": "61c4831769a96679469adaca",
                "name": "Zimbabwe",
                "icon": "Safari iCON",
                "imageFlag": "Zimbabwe Flag",
                "__v": 0,
                "id": "61c4831769a96679469adaca"
            },
            {
                "_id": "61c4832f69a96679469adacc",
                "name": "Zambia",
                "icon": "Safari iCON",
                "imageFlag": "Zambia Flag",
                "__v": 0,
                "id": "61c4832f69a96679469adacc"
            },
            {
                "_id": "61c4836369a96679469adace",
                "name": "Tanzania",
                "icon": "Safari iCON",
                "imageFlag": "Tanzania Flag",
                "__v": 0,
                "id": "61c4836369a96679469adace"
            }
        ]
    }
}

Answer 1

Your response data to class/interface is as below:

export interface ICountryListResponse {
  status: string;
  results: number;
  data: { data: Country[] };
}

Modify your CountriesService.getCountries() to expect received ICountryListResponse data response and next with .pipe(map) to return the result as Observable<Country[]>.

countries.services.ts

import { map } from 'rxjs/operators';

getCountries(): Observable<Country[]> {
  return this.http
    .get<ICountryListResponse>('http://127.0.0.1:3300/api/v1/countries/')
    .pipe(map((response: ICountryListResponse) => response.data.data));
}

Sample Demo on StackBlitz