Dart 언어 오답노트 : 37. map(), Iterable, toList()

샤워실의 바보·2023년 11월 13일
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Dart 언어 오답노트(With Chat GPT 4.0)

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

void main() async {
  final api = await ApiService().getTodaysToons();
  for (var webtoon in api) {
    print('Title: ${webtoon.title}, ID: ${webtoon.id}, Thumbnail: ${webtoon.thumb}');
  }
}

class ApiService {
  final String baseUrl = "https://webtoon-crawler.nomadcoders.workers.dev";
  
  Future<List<WebtoonModel>> getTodaysToons() async {
    final url = Uri.parse('$baseUrl/today');
    final response = await http.get(url);

    if (response.statusCode != 200) {
      throw Exception('Failed to load webtoons');
    }

    final webtoons = jsonDecode(response.body) as List;
    return webtoons.map((json) => WebtoonModel.fromJson(json)).toList();
  }
}

class WebtoonModel {
  final String title, thumb, id;
  
  WebtoonModel.fromJson(Map<String, dynamic> json)
    : title = json['title'],
      thumb = json['thumb'],
      id = json['id'];
}

List.map과 Iterable.toList를 사용하는 방식은 Dart에서 데이터 컬렉션을 변환하는 효율적인 방법입니다. 여기서는 webtoonInstances에 웹툰을 추가하는 과정에서 이 방법을 사용했습니다. 이 방식의 작동 원리를 구체적으로 살펴보겠습니다.

List.map 함수

  • List.map은 리스트의 각 요소에 함수를 적용하고 결과를 새로운 Iterable로 반환합니다.
  • 이 함수는 리스트의 각 요소를 반복하면서 주어진 함수를 적용합니다.
  • 결과는 변환된 요소들의 Iterable입니다. 이 Iterable은 지연 계산되며, 실제 값이 필요할 때까지 계산을 연기합니다.

Iterable.toList 함수

  • Iterable.toList는 Iterable을 List로 변환합니다.
  • Iterable은 일반적으로 한 번만 순회할 수 있는 반면, List는 여러 번 순회할 수 있으며, 인덱스를 통해 특정 요소에 접근할 수 있습니다.

사용 예시

final webtoons = jsonDecode(response.body) as List;
return webtoons.map((json) => WebtoonModel.fromJson(json)).toList();

위 코드에서 jsonDecode(response.body)는 JSON 데이터를 Dart 객체로 변환합니다. 변환된 결과는 List<dynamic> 형태의 webtoons 변수에 저장됩니다. 이 리스트의 각 요소는 웹툰을 나타내는 JSON 객체입니다.

  • webtoons.map((json) => WebtoonModel.fromJson(json)):

    • map 함수는 webtoons 리스트의 각 JSON 객체에 WebtoonModel.fromJson 함수를 적용합니다.
    • 결과적으로, 원래의 JSON 객체들은 WebtoonModel 객체들로 변환됩니다. 이 때 생성되는 것은 Iterable<WebtoonModel>입니다.

  • .toList():

    • toList는 이 Iterable<WebtoonModel>를 List<WebtoonModel>로 변환합니다.
    • 결과적으로, 변환된 웹툰 모델의 리스트가 반환됩니다.
Title: 소녀의 세계, ID: 654774, Thumbnail: https://image-comic.pstatic.net/webtoon/654774/thumbnail/thumbnail_IMAG21_4048794550434817075.jpg
Title: 백수세끼, ID: 733074, Thumbnail: https://image-comic.pstatic.net/webtoon/733074/thumbnail/thumbnail_IMAG21_80df3e76-47af-4007-b57c-e8f2830835e5.jpg
Title: 신의 탑, ID: 183559, Thumbnail: https://image-comic.pstatic.net/webtoon/183559/thumbnail/thumbnail_IMAG21_5f3fec31-5c95-4afe-a73f-3046288edb47.jpg
Title: 윈드브레이커, ID: 602910, Thumbnail: https://image-comic.pstatic.net/webtoon/602910/thumbnail/thumbnail_IMAG21_e861f2cf-6157-4d33-8e02-7b4cbf0a8baf.jpg
Title: 장씨세가 호위무사, ID: 728750, Thumbnail: https://image-comic.pstatic.net/webtoon/728750/thumbnail/thumbnail_IMAG21_47c21251-b213-4882-bacc-15adce1acfc8.jpg
Title: 물어보는 사이, ID: 772725, Thumbnail: https://image-comic.pstatic.net/webtoon/772725/thumbnail/thumbnail_IMAG21_a3d729eb-6ba8-4fef-aaba-7cab0ee9c8df.jpg
Title: 순정말고 순종, ID: 761461, Thumbnail: https://image-comic.pstatic.net/webtoon/761461/thumbnail/thumbnail_IMAG21_e3c857a7-900b-4085-969a-75d9127b5a38.jpg
Title: 별난식당, ID: 806189, Thumbnail: https://image-comic.pstatic.net/webtoon/806189/thumbnail/thumbnail_IMAG21_292de414-bd9a-418d-a4e9-d97060398223.jpg
Title: 어린이집 다니는 구나, ID: 817945, Thumbnail: https://image-comic.pstatic.net/webtoon/817945/thumbnail/thumbnail_IMAG21_120ad315-8518-4430-bb30-739654b49635.jpg
Title: 절대검감, ID: 796075, Thumbnail: https://image-comic.pstatic.net/webtoon/796075/thumbnail/thumbnail_IMAG21_31f75c4c-81c9-454a-8d92-9e23b577e1a5.jpg
Title: 2023 루키 단편선, ID: 816636, Thumbnail: https://image-comic.pstatic.net/webtoon/816636/thumbnail/thumbnail_IMAG21_0aaf3571-5f8a-4b86-a086-b038a27e3aed.jpg
Title: 악당 가족이 독립을 반대한다, ID: 817365, Thumbnail: https://image-comic.pstatic.net/webtoon/817365/thumbnail/thumbnail_IMAG21_fa059a74-ca14-4a89-b0d7-841a0c85139a.jpg
Title: 개같이 탈출, ID: 814594, Thumbnail: https://image-comic.pstatic.net/webtoon/814594/thumbnail/thumbnail_IMAG21_8746b12b-566e-4375-b0ab-1eaf48e17a1d.jpg
Title: 오빠집이 비어서, ID: 780414, Thumbnail: https://image-comic.pstatic.net/webtoon/780414/thumbnail/thumbnail_IMAG21_fc2621b0-84c3-404d-a18d-5925dba6ab77.jpg
Title: 시한부의 아이까지 뺏으려 합니다, ID: 814362, Thumbnail: https://image-comic.pstatic.net/webtoon/814362/thumbnail/thumbnail_IMAG21_16247d91-5c88-43aa-80e3-f28b2daf868d.jpg
Title: 칼가는 소녀, ID: 730174, Thumbnail: https://image-comic.pstatic.net/webtoon/730174/thumbnail/thumbnail_IMAG21_5bfd08ed-6ca8-4a27-9fab-d9fb15588d3a.jpg
Title: 아슈타르테, ID: 798277, Thumbnail: https://image-comic.pstatic.net/webtoon/798277/thumbnail/thumbnail_IMAG21_f3e49f1a-befe-435f-bf83-845d8516a82b.jpg
Title: ㅋㅋ단편.zip, ID: 814541, Thumbnail: https://image-comic.pstatic.net/webtoon/814541/thumbnail/thumbnail_IMAG21_18a2bffa-6c6e-4884-ab41-45b4646cabe3.jpg
Title: 결혼생활 그림일기, ID: 741891, Thumbnail: https://image-comic.pstatic.net/webtoon/741891/thumbnail/thumbnail_IMAG21_47b971e4-00b6-451b-862e-1060bae5a80d.jpg
Title: 천재 타자가 강속구를 숨김, ID: 807775, Thumbnail: https://image-comic.pstatic.net/webtoon/807775/thumbnail/thumbnail_IMAG21_91cb8ff9-5be3-40ba-8df9-661972577cd2.jpg
Title: 제국 제일의 상속녀가 되었습니다, ID: 814566, Thumbnail: https://image-comic.pstatic.net/webtoon/814566/thumbnail/thumbnail_IMAG21_4f97cbfb-8e3e-445d-848c-ae270c22f5b0.jpg
Title: 제왕, ID: 783535, Thumbnail: https://image-comic.pstatic.net/webtoon/783535/thumbnail/thumbnail_IMAG21_4b6a83cd-a5e9-408f-bbac-244f25240394.jpg
Title: 날 먹는 건 금지양!, ID: 817019, Thumbnail: https://image-comic.pstatic.net/webtoon/817019/thumbnail/thumbnail_IMAG21_6845792d-40db-4cd9-ab7a-9b86995f3383.jpg
Title: 입술이 예쁜 남자, ID: 791629, Thumbnail: https://image-comic.pstatic.net/webtoon/791629/thumbnail/thumbnail_IMAG21_4122541015824753209.jpg
Title: 루루라라 우리네 인생, ID: 802039, Thumbnail: https://image-comic.pstatic.net/webtoon/802039/thumbnail/thumbnail_IMAG21_a7a82a34-586c-4acf-b6f2-ab052be786f1.jpg
Title: 컨트롤X, ID: 812403, Thumbnail: https://image-comic.pstatic.net/webtoon/812403/thumbnail/thumbnail_IMAG21_bc35a097-4b19-43bf-849e-26f8712bd65f.jpg
Title: 더블클릭, ID: 769663, Thumbnail: https://image-comic.pstatic.net/webtoon/769663/thumbnail/thumbnail_IMAG21_935bf47d-9219-4f45-8a58-d5a7af13ce51.jpg
Title: 히어로메이커, ID: 21815, Thumbnail: https://image-comic.pstatic.net/webtoon/21815/thumbnail/thumbnail_IMAG21_7292511306663934265.jpg
Title: 피폐물의 해피엔딩을 위하여, ID: 805437, Thumbnail: https://image-comic.pstatic.net/webtoon/805437/thumbnail/thumbnail_IMAG21_e830e751-20be-4c57-a6ff-f299588d05b6.jpg
Title: 서브 남주가 파업하면 생기는 일, ID: 803518, Thumbnail: https://image-comic.pstatic.net/webtoon/803518/thumbnail/thumbnail_IMAG21_32d146f5-7e22-4fe4-bc73-92b2e446d7f7.jpg
Title: 악당과 악당이 만나면, ID: 804782, Thumbnail: https://image-comic.pstatic.net/webtoon/804782/thumbnail/thumbnail_IMAG21_f09967ec-e4e8-4fb8-a8d5-a65db4c6e14e.jpg
Title: 오늘의 일기예보, ID: 817987, Thumbnail: https://image-comic.pstatic.net/webtoon/817987/thumbnail/thumbnail_IMAG21_22f8f0f6-ffb1-4b24-b47e-6a1d33074ead.jpg
Title: 엘프, ID: 808776, Thumbnail: https://image-comic.pstatic.net/webtoon/808776/thumbnail/thumbnail_IMAG21_fb25d2f3-790c-48db-beaf-c2504f4ed4c0.jpg
Title: 사이다걸, ID: 800333, Thumbnail: https://image-comic.pstatic.net/webtoon/800333/thumbnail/thumbnail_IMAG21_407ea651-d14f-47af-9e06-8813e7160421.jpeg
Title: 너를 돌려차는 방법, ID: 802551, Thumbnail: https://image-comic.pstatic.net/webtoon/802551/thumbnail/thumbnail_IMAG21_04fdcd36-c440-4feb-8b3d-573b3584a32f.jpg
Title: 세번째 로망스, ID: 796368, Thumbnail: https://image-comic.pstatic.net/webtoon/796368/thumbnail/thumbnail_IMAG21_9f304f70-bc24-4cdc-b582-8d1b63d013e0.jpg
Title: 라서드, ID: 756140, Thumbnail: https://image-comic.pstatic.net/webtoon/756140/thumbnail/thumbnail_IMAG21_7c527b6e-773f-40c8-aa1a-5cbd9e7dc482.jpg
Title: 원하나, ID: 804469, Thumbnail: https://image-comic.pstatic.net/webtoon/804469/thumbnail/thumbnail_IMAG21_2aa7b888-6149-4ba0-ae84-0158fd0e249c.jpeg
Title: 영앤리치가 아니야!, ID: 734574, Thumbnail: https://image-comic.pstatic.net/webtoon/734574/thumbnail/thumbnail_IMAG21_8688bbf6-1067-465b-9070-4fef7c1ab1cd.jpg
Title: 고백어택, ID: 807397, Thumbnail: https://image-comic.pstatic.net/webtoon/807397/thumbnail/thumbnail_IMAG21_d0a7cee2-4ded-4506-aedf-71c25675247c.jpg
Title: 백호랑, ID: 745654, Thumbnail: https://image-comic.pstatic.net/webtoon/745654/thumbnail/thumbnail_IMAG21_3978989878055821874.jpg
Title: 집사, 주세요!, ID: 802033, Thumbnail: https://image-comic.pstatic.net/webtoon/802033/thumbnail/thumbnail_IMAG21_ccce5530-0976-4a0d-b76c-d54c5620cdd5.jpg
Title: 루크 비셸 따라잡기, ID: 794939, Thumbnail: https://image-comic.pstatic.net/webtoon/794939/thumbnail/thumbnail_IMAG21_23006afc-accd-46f6-8014-c955c4aa6241.jpg
Title: 꿈의 기업, ID: 687915, Thumbnail: https://image-comic.pstatic.net/webtoon/687915/thumbnail/thumbnail_IMAG21_d46ad6b8-e9a8-4bc8-b501-e62adfee0eb6.jpg
Title: 파견체, ID: 791256, Thumbnail: https://image-comic.pstatic.net/webtoon/791256/thumbnail/thumbnail_IMAG21_3833187132113172581.jpg
Title: 하루의 하루, ID: 774302, Thumbnail: https://image-comic.pstatic.net/webtoon/774302/thumbnail/thumbnail_IMAG21_4121973654889457249.jpg
Title: 어느날 짝남에게 공작님이 빙의했다, ID: 816528, Thumbnail: https://image-comic.pstatic.net/webtoon/816528/thumbnail/thumbnail_IMAG21_12b8af45-dcdb-4a37-8ccf-b597e490e55c.jpg
Title: 북부 공작님을 유혹하겠습니다, ID: 794421, Thumbnail: https://image-comic.pstatic.net/webtoon/794421/thumbnail/thumbnail_IMAG21_65e1c328-a2e5-42f6-86ef-47d7424bb44e.jpg
Title: 메리의 불타는 행복회로, ID: 797253, Thumbnail: https://image-comic.pstatic.net/webtoon/797253/thumbnail/thumbnail_IMAG21_3adf296f-505b-4824-98b0-61c28432fb2d.jpg
Title: 최후의 금빛아이, ID: 772734, Thumbnail: https://image-comic.pstatic.net/webtoon/772734/thumbnail/thumbnail_IMAG21_fdecfea5-8ca1-4a32-9c55-34a30f24266d.jpg
Title: 마이너스의 손, ID: 679568, Thumbnail: https://image-comic.pstatic.net/webtoon/679568/thumbnail/thumbnail_IMAG21_0e7abd73-060d-42eb-afed-65cafc457104.jpg
Title: 토마토가 돼라!, ID: 805702, Thumbnail: https://image-comic.pstatic.net/webtoon/805702/thumbnail/thumbnail_IMAG21_23e30a03-98e2-4a72-a161-49bf171d1d08.jpeg
Title: 결혼공략, ID: 792317, Thumbnail: https://image-comic.pstatic.net/webtoon/792317/thumbnail/thumbnail_IMAG21_524ed207-a4c2-4864-b8e1-3aef96a7ba41.jpg
Title: 모스크바의 여명, ID: 772243, Thumbnail: https://image-comic.pstatic.net/webtoon/772243/thumbnail/thumbnail_IMAG21_3918807214864216674.jpg
Title: 역주행!, ID: 776256, Thumbnail: https://image-comic.pstatic.net/webtoon/776256/thumbnail/thumbnail_IMAG21_d520a876-7403-4349-a56a-f1203882bed2.jpg
Title: 슈퍼스타 천대리, ID: 785749, Thumbnail: https://image-comic.pstatic.net/webtoon/785749/thumbnail/thumbnail_IMAG21_7d010b0f-a77f-4449-a910-1816e2c547cc.jpg
Title: 매지컬 급식:암살법사, ID: 791062, Thumbnail: https://image-comic.pstatic.net/webtoon/791062/thumbnail/thumbnail_IMAG21_d358a9ab-09bc-436b-8a77-076cae2ea8d1.jpg
Title: 러브 똘츄얼리, ID: 811129, Thumbnail: https://image-comic.pstatic.net/webtoon/811129/thumbnail/thumbnail_IMAG21_02284133-0eb0-407a-9c4e-7381dbd7a8a4.jpg
Title: 행운을 부탁해!, ID: 799868, Thumbnail: https://image-comic.pstatic.net/webtoon/799868/thumbnail/thumbnail_IMAG21_edfa4344-9f13-4a6c-8b9f-00d08cf37a1d.jpg
Title: 버그이터, ID: 793067, Thumbnail: https://image-comic.pstatic.net/webtoon/793067/thumbnail/thumbnail_IMAG21_3544444194497192757.jpg
Title: 악취해결사, ID: 807600, Thumbnail: https://image-comic.pstatic.net/webtoon/807600/thumbnail/thumbnail_IMAG21_f1a481c2-78fb-433d-8db4-01e31b150755.jpg
Title: 중독연구소, ID: 740132, Thumbnail: https://image-comic.pstatic.net/webtoon/740132/thumbnail/thumbnail_IMAG21_d6f6e062-23d4-432a-a4be-6e1e66f63ede.jpg

이 방식은 코드를 간결하게 만들 뿐만 아니라, 데이터 변환 과정을 보다 선언적이고 이해하기 쉽게 만듭니다.

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Dart 오답노트 38 : Map, Object, 다형성(Polymorphism)

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