Unsplash Api call in Dart example.dart

import 'dart:convert';
import 'package:http/http.dart' as http;

abstract class PhotosRepository {
  Future<List<Photo>> getPhotosList();
}

class Photo {
  Photo({
    this.id,
    this.title,
    this.username,
    this.url,
  });

  factory Photo.fromJson(Map<String, dynamic> json) {
    return Photo(
      id: json['id'] as String,
      title: json['alt_description'] as String,
      username: json['user']['name'] as String,
      url: json['urls']['raw'] as String,
    );
  }

  final String id;
  final String title;
  final String username;
  final String url;

  @override
  String toString() {
    return '''$id, $title, $username, $url''';
  }
}

class UnsplashApi {
  final String _clientId = "xxxxxxxxxxxxx";

  Future<String> _fetch(String url) async {
    try {
      url = buildUrl(url);
      final http.Response response = await http.get(url);
      if (response.statusCode == 200) {
        return response.body;
      }
      return null;
    } catch (e) {
      print(e);
      return null;
    }
  }

  Future<dynamic> fetchDataByUrl(String url) async {
    final String data = await _fetch(url);
    try {
      return json.decode(data);
    } catch (e) {
      print('Bad content, could not decode JSON $e');
    }
  }

  String buildUrl(String url) {
    return url.contains('?') ? '$url&client_id=$_clientId' : '$url?client_id=$_clientId';
  }
}

class UnsplashPhotosRepository implements PhotosRepository {
  UnsplashPhotosRepository(this._api);

  final UnsplashApi _api;
  final String _url = 'https://api.unsplash.com/photos';

  @override
  Future<List<Photo>> getPhotosList() async {
    final dynamic result = await _api.fetchDataByUrl(_url);
    return (result as List<dynamic>)?.map((dynamic el) => Photo.fromJson(el as Map<String, dynamic>))?.toList();
  }
}

void main() {
  (() async {
    final List<Photo> m = await UnsplashPhotosRepository(UnsplashApi()).getPhotosList();
    print(m);
  }());
}