Flutter: json_serializable type '_InternalLinkedHashMap<Object?, Object?>' is not a subtype of type 'Map<String, dynamic>' error

Question

I am linking cloud function to my Flutter model. Result is coming from Cloud-Function

  print(result.data);
  print(result.data.runtimeType);
  GameModel _incomingGame = GameModel.fromJson(result.data);

print(result.data);

{
    game: 'GTA',
    played: ['ISODATE', ...]
}

print(result.data.runtimeType);

flutter: _InternalLinkedHashMap<String, dynamic>

GameModel

@JsonSerializable()
class GameModel {
  String? game;
  List? played;

  GameModel(
      this.game,
      this.played,);

  factory GameModel.fromJson(Map<String, dynamic> json) =>
      _$GameModelFromJson(json);

  Map<String, dynamic> toJson() => _$GameModelToJson(this);
}

game_model.g.dart

// GENERATED CODE - DO NOT MODIFY BY HAND

part of 'game_model.dart';

// **************************************************************************
// JsonSerializableGenerator
// **************************************************************************

GameModel _$GameModelFromJson(Map<String, dynamic> json) => GameModel(
      json['game'] as String?,
      json['played'] as List?,
    );

Map<String, dynamic> _$GameModelToJson(GameModel instance) => <String, dynamic>{
      'game': instance.game,
      'played': instance.played,
    };

The incoming data result's runtimeType shows that it is Map<String, dynamic> in the console. However, when I execute GameModel.fromJson(), it causes type '_InternalLinkedHashMap<Object?, Object?>' is not a subtype of type 'Map<String, dynamic>' in type cast.

I really don't get that why this is happening somehow? Even if I do something like below also causes the same type cast error.

GameModel _gameData = result.data;
var game = GameModel.fromJson(_gameData);

Is there any way that I can fix this?

you can try with jsonDecode, like GameModel.fromJson(jsonDecode(result.data)); — Jahidul Islam
– Jahidul Islam, Commented Dec 6, 2021 at 5:18
jsonDecode(result.data) returns '_InternalLinkedHashMap<String, dynamic>' is not a subtype of type 'String' error. — chichi
– chichi, Commented Dec 6, 2021 at 5:45

聂超群 · Accepted Answer · 2021-12-06 06:34:58Z

2

Try this solution:

GameModel.fromJson((result.data as Map<dynamic, dynamic>).cast<String, dynamic>())

answered Dec 6, 2021 at 6:34

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Comments

Sajad Abdollahi · Accepted Answer · 2021-12-06 07:10:26Z

1

Try these solutions

  GameModel _incomingGame = GameModel.fromJson(result.data as Map<String, dynamic>);

Or

  GameModel _incomingGame = GameModel.fromJson(Map<String, dynamic>.from(result.data));

It also would be better if you check the types before executing type casts

If above solutions doesn't work, add the type when calling cloud functions

final func = FirebaseFunctions.instance.httpsCallable('gameFunction');
final result = await func<Map<String, dynamic>?>();

edited Dec 6, 2021 at 7:10

answered Dec 6, 2021 at 6:33

Sajad Abdollahi

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7 Comments

chichi Over a year ago

Having same problem :/ Map<String, dynamic> game = Map<String, dynamic>.from(result.data); and print(game.runtimeType); return Map<String, dynamic> but as soon as it goes into .fromJson(), it turns to Map<Object?, Object?>

Sajad Abdollahi Over a year ago

Could you write the fromJson method manually? or add the generated method to question @chichi

Sajad Abdollahi Over a year ago

Yeah that's odd, I updated the answer if you are using firebase cloud functions maybe this one works out, @chichi

chichi Over a year ago

Same stuffs. I am just restructuring result.data and just use GameModel(); to add directly to my variable. If I figure it out then I will keep ya update what was the problem bro. Thanks so much for help

chichi Over a year ago

There was one more object - map added by mongoose that coming with data as Map<Object?, Object?>... So, I've added an object to my MongoDB and all these objects are type casted as Map<Object?, Object?>.

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