How to parse json with a variable as any type cast in flutter dart

Question

Below is my JSON that i am getting in api response. I want to parse below json in flutter dart using json_serializable.

[
  {
    "id": 1,
    "email": "[email protected]",
    "gender": "Female",
    "ip_address": "101.34.28.146",
    "name": "Gerry",
    "retro": true
  },
  {
    "id": 2,
    "email": "[email protected]",
    "gender": "Male",
    "ip_address": "117.77.75.29",
    "name": "Zared",
    "retro": ""
  },
  {
    "id": 3,
    "email": "[email protected]",
    "gender": "Male",
    "ip_address": "165.84.97.206",
    "name": "Ozzy",
    "retro": true
  },
  {
    "id": 4,
    "email": "[email protected]",
    "gender": "Male",
    "ip_address": "76.73.136.113",
    "name": "Edwin",
    "retro": false
  }
]

Below is my object class form json

import 'package:json_annotation/json_annotation.dart';

@JsonSerializable()
class UserItem {
  int id;
  String email;
  String gender;
  @JsonKey(name: 'ip_address')
  String ipAddress;
  String name;
  bool retro;

  UserItem(this.id, this.email, this.gender, this.ipAddress, this.name, this.retro);

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

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

UserItem _$UserItemFromJson(Map<String, dynamic> json) => UserItem(
  json['id'] as int,
  json['email'] as String,
  json['gender'] as String,
  json['ip_address'] as String,
  json['name'] as String,
  json['retro'] as bool,
);

Map<String, dynamic> _$UserItemToJson(UserItem instance) => <String, dynamic>{
  'id': instance.id,
  'email': instance.email,
  'gender': instance.gender,
  'ip_address': instance.ipAddress,
  'name': instance.name,
  'retro': instance.retro,
};

I am unable to parse json because object at id:3 contains retro:"" and in rest of json retro is bool type. i am getting Type Cast Exception

jsonParse exception: type 'String' is not a subtype of type 'bool' in type cast

NOTE: I am using third party API solution and i am unable to ask for changes on api response to change empty string in json response with default boolean value.

Answer 1

Instead of

json['retro'] as bool

You can do

json['retro'].toString()=="true"

That way you can support both bool and string type.

Answer 2

I believe you can annotate the retro property like this:

  @JsonKey(
    fromJson: _fromJson,
  )
  bool retro;

and have this function defined:

  static bool _fromJson(dynamic value) => value?.toString() == 'true';

Answer 3

You can set the retro as a dynamic variable like this. Then you will have to cast it after fetching the data from the backend as you want the visualization to be.

import 'package:json_annotation/json_annotation.dart';

@JsonSerializable()
class UserItem {
  int id;
  String email;
  String gender;
  @JsonKey(name: 'ip_address')
  String ipAddress;
  String name;
  dynamic? retro;

  UserItem(
      this.id, this.email, this.gender, this.ipAddress, this.name, this.retro);

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

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

UserItem _$UserItemFromJson(Map<String, dynamic> json) => UserItem(
      json['id'] as int,
      json['email'] as String,
      json['gender'] as String,
      json['ip_address'] as String,
      json['name'] as String,
      json['retro'] as dynamic,
    );

Map<String, dynamic> _$UserItemToJson(UserItem instance) => <String, dynamic>{
      'id': instance.id,
      'email': instance.email,
      'gender': instance.gender,
      'ip_address': instance.ipAddress,
      'name': instance.name,
      'retro': instance.retro,
    };