How to read/write a custom nested object in Hive?

Question

I am caching a big chunk of data from API, I get it as a dynamic list which contains Map<String, dynamic>.

I can either save the dynamic list itself which I get in response or else I can save the parsed object but the object's class is nested and has many types of objects, so adding adapters to all of the custom objects is cumbersome to manage.

Is there any better way to do this?

I tried storing the list directly but it only runs when the cache is fresh, after a restart the type data is lost and I get an error:

Unhandled Exception: type '_InternalLinkedHashMap<dynamic, dynamic>' is not a subtype of type 'Map<String, dynamic>' in type cast

I referred to https://github.com/hivedb/hive/issues/522 but it didn't solve my issue.

Answer 1

TL;DR Create another factory method for fetching data from Hive.

Because of that issue, I actually include one factory method for Hive in the model class. For example, below is my HyperLink model class for preview information of a website.

class Hyperlink {
  String url;
  bool loaded;
  String? img;
  String? title;
  String? desc;
  String short;

  Hyperlink({
    required this.url,
    this.loaded = false,
    this.img,
    this.title,
    this.desc,
    required this.short,
  });

  Hyperlink copyWith({
    String? url,
    bool? loaded,
    String? img,
    String? title,
    String? desc,
    String? short,
  }) =>
      Hyperlink(
        url: url ?? this.url,
        loaded: loaded ?? this.loaded,
        img: img ?? this.img,
        title: title ?? this.title,
        desc: desc ?? this.desc,
        short: short ?? this.short,
      );

  factory Hyperlink.fromMap(Map<String, dynamic> json) => Hyperlink(
        url: json['url'],
        loaded: json['loaded'],
        img: json['img'],
        title: json['title'],
        desc: json['desc'],
        short: json['short'],
      );

  factory Hyperlink.fromHive(Map<dynamic, dynamic> json) => Hyperlink(
        url: json['url'],
        loaded: json['loaded'],
        img: json['img'],
        title: json['title'],
        desc: json['desc'],
        short: json['short'],
      );

  Map<String, dynamic> toMap() {
    return {
      'url': url,
      'loaded': loaded,
      'img': img,
      'title': title,
      'desc': desc,
      'short': short,
    }..removeWhere(
        (dynamic key, dynamic value) => key == null || value == null);
  }
}

There I have a 2 factory method, which is just fromMap and fromHive and whenever I get data from Hive I just use fromHive

In case of storing data, you can simply store a Map<String,dynamic> to hive.

Hope this helps. Thank you.

Answer 2

I solved it by saving my data as Json string instead of saving the data with their types. I used jsonEncode(data) and then while fetching it used jsonDecode(data).