How to deserialize Date ISO String to DateTime Object in built_value serialization in dart? - flutter

Question

I wanna serialize a json object including an ISOString date to a dart object using built value.
this is a sample json:
{
"title": "test",
"description": "test description",
"date": "2020-06-05T11:42:38.585Z",
"creator": {
"email": "test#test.com"
}
}
this is the model:
abstract class Post implements Built<Post, PostBuilder> {
#nullable
#BuiltValueField(wireName: '_id')
String get id;
String get title;
String get description;
DateTime get date;
#nullable
User get creator;
Post._();
static Serializer<Post> get serializer => _$postSerializer;
factory Post([updates(PostBuilder b)]) = _$Post;
factory Post.fromJson(Map<String, dynamic> map) =>
serializers.deserializeWith(Post.serializer, map);
Map<String, dynamic> toJson() =>
serializers.serializeWith(Post.serializer, this);
}
and this is the error:
Deserializing '[title, test1, description, test1 description, date, 2020-06-05T...' to
'Post' failed due to: Deserializing '2020-06-05T11:42:38.585Z' to 'DateTime' failed due
to: type 'String' is not a subtype of type 'int' in type cast
how do I fix that?

Answer 1

You can import the Iso8601DateTimeSerializer directly from built_value - don't copy the file over to your project.
Your final serializers.dart should look like:
import 'package:built_value/iso_8601_date_time_serializer.dart';
import 'package:built_value/iso_8601_duration_serializer.dart';
import 'package:built_value/serializer.dart';
import 'package:built_value/standard_json_plugin.dart';
part 'serializers.g.dart';
#SerializersFor([
// your built value classes
])
final Serializers serializers = (_$serializers.toBuilder()
..add(Iso8601DateTimeSerializer())
..add(Iso8601DurationSerializer())
..addPlugin(StandardJsonPlugin())
).build();

Answer 2

You need to add a custom DateTime serializer that you can find here: Iso8601DateTimeSerializer
create a new dart file (I named it iso8601_date_time_serializer.dart)
paste the code from 1
add the import to your serializers.dart file (import 'iso8601_date_time_serializer.dart';)
edit your serializers.g.dart file
Serializers _$serializers = (new Serializers().toBuilder()
..add(Iso8601DateTimeSerializer())
..add(Post.serializer) // I assume you have this in yours
..addPlugin(StandardJsonPlugin()))
.build();
Please note that this modification might be deleted if you regenerate the code with build_runner.
In case you want to dig deeper, I got the answer from built_value GitHub issue 454