Flutter _TypeError type 'List<dynamic>' is not a subtype of type 'Map<String, dynamic>

Question

I am facing a strange error in flutter. I am using json serialisable.

Here is my code

class DivMatches{
  final List<Match> matches;
   DivMatches(this.matches);
  factory DivMatches.fromJson(Map<String, dynamic> json) =>
  _$DivMatchesFromJson(json);
  Map<String, dynamic> toJson() => _$DivMatchesToJson(this);

}

My web api sends data like this

[
 [
   {..},
   {..},
   {..},
   {..}
 ],
[...],
[...],
[...],
[...],
[...],
[...]
]

It's array of array.

Code that is generating error is

data = body.map((el) => DivMatches.fromJson(el)).toList(); 

error it gives

Exception has occurred.
_TypeError (type 'List<dynamic>' is not a subtype of type 'Map<String, dynamic>')

Here is the screenshot

JSON DATA here is the screenshots of json data formate

Answer 1

Change this line :

final body = json.decode(res.body);

To this:

final body = json.decode(res.body) as List;

And this:

List<DivMatches> data = [];

body.forEach((el) {
   final List<Match> sublist = el.map((val) => Match.fromJson(val)).toList();
   data.add(DivMatches(sublist));
}); 

Note: check if your Match.fromJson returns a Match object or Map.

Answer 2

You can use cast<Type>():

import 'dart:convert';

void main() {
  print(getScores());
}

class Score {
  int score;
  Score({this.score});

  factory Score.fromJson(Map<String, dynamic> json) {
    return Score(score: json['score']);
  }
}

List<Score> getScores() {
  var jsonString = '''
  [
    {"score": 40},
    {"score": 80}
  ]
''';

  List<Score> scores = jsonDecode(jsonString)
      .map((item) => Score.fromJson(item))
      .toList()
      .cast<Score>(); // Solve Unhandled exception: type 'List<dynamic>' is not a subtype of type 'List<Score>'

  return scores;
}