How can i cast a dart map <String, dynamic> to <String, List<List<int>>>?

Question

I read up some data from shared prefs and jsonDecode it into a variable called shapes. When I inspect the shapes in the debugger it looks like the right type. But when I assign it to the following variable "theShapes" I get errors such as Unhandled Exception: type '_InternalLinkedHashMap<dynamic, dynamic>' is not a subtype of type 'Map<String, List<List<int>>>'

static var theShapes = <String, List<List<int>>>{

'general': [
  [1, 0, 1, 0, 1, 0, 1, 0, 1, 0],
  [0, 1, 0, 1, 0, 1, 0, 1, 0, 1],
  [1, 0, 1, 0, 1, 0, 1, 0, 1, 0],
  [0, 1, 0, 1, 0, 1, 0, 1, 0, 1],
  [1, 0, 1, 0, 1, 0, 1, 0, 1, 0],
  [0, 1, 0, 1, 0, 1, 0, 1, 0, 1],
  [1, 0, 1, 0, 1, 0, 1, 0, 1, 0],
  [0, 1, 0, 1, 0, 1, 0, 1, 0, 1],
  [1, 0, 1, 0, 1, 0, 1, 0, 1, 0],
  [0, 1, 0, 1, 0, 1, 0, 1, 0, 1],
],
....
};

The code used to try to cast the "shapes" variable to the type of "theShapes" is like this at the moment:

 theShapes = shapes
      .map((key, value) => MapEntry(key, List.castFrom(value).toList()));

Try this: final shapesMap = shapes.map((key, value) => MapEntry(key, List<List<int>>.from(value))); theShapes = Map<String, List<List<int>>>.from(shapesMap); — Mol0ko
– Mol0ko, Commented Nov 18, 2020 at 9:20
Nice try but that code throws this error: Unhandled Exception: type 'List<dynamic>' is not a subtype of type 'List<int>' on the first line. — lost baby
– lost baby, Commented Nov 18, 2020 at 11:02

Yadhu · Accepted Answer · 2020-11-18 09:47:59Z

1

here you go



go(String data){
  final decodedData = jsonDecode(data);
  if(decodedData is Map){
    return decodedData.map<String,List<List<int>>>((key, value) => MapEntry(key as String, (value as List).map<List<int>>((e) => (e as List).map<int>((i) => i as int).toList()).toList()));
  }
  return null;
}

edited Nov 18, 2020 at 9:47

answered Nov 18, 2020 at 9:13

Yadhu

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