Problem saving and restoring list of string

[dadokkio]

If I save a List<String> I'm able to use and modify it during app run but at the following restart the app crashes with error:

type 'List<dynamic>' is not a subtype of type 'List<String>?' in type cast

There is something I need to specify during write or read to manage list properly?

My actual code to restore:

  @override
  void initState() {
    super.initState();
    try {
      _savedDevices = box.read('saved_devices') ?? <String>[];
    } catch (e) {
      List<dynamic> tmp = box.read('saved_devices');
      _savedDevices = tmp.map((item) => item.toString()).toList();
    }
  }

where _savedDevices is a List<String> saved as box.write('saved_devices', _savedDevices);

Thanks

[Vlad-Adrian]

I have the same issue, unfortunately couldn't find a workaround for now. @jonataslaw any help please?

[markst]

Also experiencing a similar issue. Works fine first time round, but fails after relaunch with the following:

Unhandled Exception: type 'List<dynamic>' is not a subtype of type 'List<Map<String, String>>?' in type cast E/flutter (19263): #0 StorageImpl.read 

I'm attempting to store values in a list of maps:

final _downloads = ReadWriteValue("downloads", List<Map<String, String>>.empty(growable: true), () => GetStorage('downloads'));

[markst]

@Vlad-Adrian wonder if a workaround could be to cast to List<dynamic> then cast back when writing?

    try {
      List<dynamic> downloads = _downloads.val;
      downloads.add(tags);
      _downloads.val = downloads as List<Map<String, String>>;
    } catch (t) {
      print(t);
    }

[Vlad-Adrian]

@markst so you are having an issue when writing?

It is strange that you have problems when writing. Did you try with Get.write(key, value); and read it back with Get.read(key);? When you read it back from memory you can cast it from dynamic to String and should be fine. It doesn't matter if you cast it to String when you save(write) it, after an app restart, the type will get lost.

I hope it helps. In any case let me know :)

[Apollo108]

I also had strange behaviour while saving List, and now I always encode it to a string, and then decode it back (e.g.: List.from(json.decode(map['integers'] as String) as List)). Works fine.

[WingCH]

My Solution

write

Future<void> saveImageList(List<ImageModel> imageModels) async {
      List<Map<String, dynamic>> rawData =
          imageModels.map((e) => e.toJson()).toList();
      await box.write(imageListsKey, rawData);
  }

read

List<dynamic>? result = box.read(imageListsKey);
if(result != null) {
List<ImageModel> modelList = result.map<ImageModel>((element) {
          return ImageModel.fromJson(element);
        }).toList();
}

[songgnqing]

_savedDevices = box.read<List<dynamic>>('saved_devices').cast<String>() ?? <String>[];

json.decode a list return List<dynamic>. You need to call cast to change the item type form dynamic to String.