type '(dynamic) => dynamic' is not a subtype of type '(dynamic) => bool' of 'test' when I use map function

Question

I have a StatefulWidget widget with a LinkedHashMap member done like this:

LinkedHashMap _items = new LinkedHashMap<String, List<dynamic>>();

Now I need to filter the items inside the List<dynamic> items of the Map.

I use this code to filter:

function filter(_items) {
    return _items.map((day, items) {
        return new MapEntry(day, items.where((i) {
          return i.stringProperty.contains(widget.filter);
        }).toList());
    });
}

But I get the error in the subject

type '(dynamic) => dynamic' is not a subtype of type '(dynamic) => bool' of 'test'

Answer 1

I solved with this code:

function filter(_items) {
    return _items.map((day, items) {
        return new MapEntry(day, items.where((i) {
          return i.stringProperty.contains(widget.filter) ? true : false;
        }).toList());
    });
}

It seems the contains function does not return a bool value.