_CastError (type '_CompactIterable<dynamic>' is not a subtype of type 'List<dynamic>' in type cast)

Question

I want to deserialize JSON files using this model but this problem occurred. If I am wrong deserialize the file. What is the proper technique to deserialize the file and show the key name like (Thriller, Actions,..) in list-view and by clicking that listview It would display movies-name in grid-view.

This is a local json file structure

{
  "Thriller": [
    {
      "Death Clique": "https://www.youtube.com/watch?v=4Q9lTjqQeBU&ab_channel=VMovies"
    },
    {
      "CID": "https://www.youtube.com/watch?v=4Q9lTjqQeBU&ab_channel=VMovies"
    },
    {
      "Wrong Turn": "https://www.youtube.com/watch?v=9spc-dExLH0&ab_channel=SagarForever"
    },
    
  ],
  "Action Movie": [
    {
      "Nobody": "https://nobodymovie.com"
    },
    {
      "Tenet": "https://tenetmovie.com"
    },
    
  ],
  "Romantic Movie": [
    {
      "Titanic": "https://titanicmovie.com"
    },
    {
      "The Vow": "https://thevowmovie.com"
    },
    
  ]
}

This is the model of the json file.

class MovieCategories {
  final String? title;
  final List<Movie>? subServices;

  MovieCategories({ this.title, this.subServices});

  factory MovieCategories.fromJson(Map<String, dynamic> json) {
     var list = json.values as List;
    List<Movie> imagesList = list.map((i) => Movie.fromJson(i)).toList();

    return MovieCategories(
      title: json.keys.toString(),
      subServices: imagesList,
    );
  }
}
class Movie {
  final String? title;
  final String? url;

  Movie({this.title, this.url});

  factory Movie.fromJson(Map<String, dynamic> parsedJson){
   return Movie(
     title:parsedJson.keys.toString(),
     url:parsedJson.values.toString()
   );
  }
}

API call :

class FetchData {
  static final List<MovieCategories> data = [];
  static Future<String> _loadAddressAsset() async {
    return await rootBundle.loadString('assets/json/movie-categories.json');
  }

  static Future<List<MovieCategories>> loadAddress() async {
    data.clear();
    final jsonAddress = await _loadAddressAsset();
    final jsonResponse = json.decode(jsonAddress);
    data.add(MovieCategories.fromJson(jsonResponse));
    print(data);
    return data;
  }
}

Answer 1

Your problem is this line:

var list = json.values as List;

Map.values isn't a List, it's an Iterable. If you want it as a list, you need to convert it:

var list = json.values.toList();