我正在制作一个Flutter应用程序,我正在使用The MovieDB api来获取数据.当我打电话给api并要求一部特定的电影时,这是我得到的一般格式：
{
"adult": false,"backdrop_path": "/wrqUiMXttHE4UBFMhLHlN601MZh.jpg","belongs_to_collection": null,"budget": 120000000,"genres": [
{
"id": 28,"name": "Action"
},{
"id": 12,"name": "Adventure"
},{
"id": 878,"name": "Science Fiction"
}
],"homepage": "http://www.rampagethemovie.com","id": 427641,"imdb_id": "tt2231461","original_language": "en","original_title": "Rampage",...
}
我已经设置了一个模型类来解析它,并且类定义如下：
import 'dart:async';
class MovieDetail {
final String title;
final double rating;
final String posterArtUrl;
final backgroundArtUrl;
final List<Genre> genres;
final String overview;
final String tagline;
final int id;
const MovieDetail(
{this.title,this.rating,this.posterArtUrl,this.backgroundArtUrl,this.genres,this.overview,this.tagline,this.id});
MovieDetail.fromJson(Map jsonMap)
: title = jsonMap['title'],rating = jsonMap['vote_average'].toDouble(),posterArtUrl = "http://image.tmdb.org/t/p/w342" + jsonMap['backdrop_path'],backgroundArtUrl = "http://image.tmdb.org/t/p/w500" + jsonMap['poster_path'],genres = (jsonMap['genres']).map((i) => Genre.fromJson(i)).toList(),overview = jsonMap['overview'],tagline = jsonMap['tagline'],id = jsonMap['id'];
}
class Genre {
final int id;
final String genre;
const Genre(this.id,this.genre);
Genre.fromJson(Map jsonMap)
: id = jsonMap['id'],genre = jsonMap['name'];
}
我的问题是我无法从JSON中正确解析该类型.当我获得JSON并将其传递给我的模型类时,我收到以下错误：
I/flutter (10874): type 'List<dynamic>' is not a subtype of type 'List<Genre>' where I/flutter (10874): List is from dart:core I/flutter (10874): List is from dart:core I/flutter (10874): Genre is from package:flutter_app_first/models/movieDetail.dart
我认为这会有效,因为我为Genre对象创建了一个不同的类,并将JSON数组作为列表传递.我不明白List< dynamic>不是List< Genre>的孩子因为关键字动态不是暗示任何对象吗？有谁知道如何将嵌套的JSON数组解析为自定义对象？
解决方法
尝试genres =(jsonMap [‘genres’]作为List).map((i)=> Genre.fromJson(i)).toList()
问题：调用没有强制转换的map会使它成为动态调用,这意味着Genre.fromJson的返回类型也是动态的(不是流派).
看一下https://flutter.io/json/的一些提示.
像https://pub.dartlang.org/packages/json_serializable这样的解决方案使这更容易
