Support `freezed` entities

[msxenon]

Hello,
as far as I know in objectbox-dart we can't create an immutable class.

I have used @freezed with "HiveDB" but I wish we can achieve that with object box

Example:

part 'priority_entity.freezed.dart';
part 'priority_entity.g.dart';

@freezed
abstract class PriorityEntity with _$PriorityEntity {
  @HiveType(typeId: 2, adapterName: 'PriorityEntityAdapter')
  const factory PriorityEntity({
    @required @HiveField(0) String id,
    @required @HiveField(1) @JsonKey(name: 'org_id') String orgId,
    @required @HiveField(2) String name,
    @required @HiveField(3) bool active,
    @required @HiveField(4) List<PriorityStates> states,
  }) = _PriorityEntity;

  factory PriorityEntity.fromJson(Map<String, dynamic> json) =>
      _$PriorityEntityFromJson(json);
}

---

edit by @vaind: fix the code block

[vaind]

It seems like it could almost work (with the new yet-unreleased support for final fields), with the following declaration:

@freezed
class Person with _$Person {
  @Entity()
  factory Person({ @Id(assignable: true) int? id, String? name, int? age }) = _Person;
}

However, with the freezed generated class being private (_$_Person), it currently cannot be accessed from the objectbox.g.dart. In order to support this, we'd need to switch generated code to use part/part of. And because that would also be necessary if users wanted to store private fields, it might just make sense. Let's consider (the prep work) for 1.0.

[vaind]

I've had a look at what's available in the context when the generator runs... There doesn't seem to be any easy-to-get-to info whether the file is a library with parts or a single-file library, but there is file content so we can check manually - for each entity, the following should lead to the source file: element.enclosingElement.source.

Therefore, we can do this post 1.0 without breaking compatibility for existing users. If others would like to see this feature, please upvote the original issue description (not this comment :) ).

[Buggaboo]

freezed? frozen? Or shall we let grammar go...

[vaind]

freezed? frozen? Or shall we let grammar go...

That's the name of an existing package, not an annotation we'd add to ObjectBox. But yeah, I was a bit flabbergasted by the name myself...

[greenrobot]

freezed? frozen? Or shall we let grammar go...

👍 Definitely! https://www.youtube.com/watch?v=L0MK7qz13bU