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'

Similar problem with Dart version 2.7.2, and the ternary operator trick solves it. I am not even using a function like `contains`, but a straight boolean test (`a>0`). Perhaps some bug or regression somewhere. BTW the `test` is the callback passed to `where`, according to the [language reference](https://api.dart.dev/stable/2.7.2/dart-collection/ListMixin/where.html). — Eric Platon, Apr 20 '20 at 06:18

score 11 · Accepted Answer · answered Dec 15 '19 at 15:08

11

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.

answered Dec 15 '19 at 15:08

Giacomo M

4,450
7
28
57

1

`contains` does indeed return a boolean. Something else is interfering. – Randal Schwartz Dec 16 '19 at 02:06
@RandalSchwartz the solution that worked is pretty clear, the problem was the return value of the contains function. I am not able to find out something that interferes. – Giacomo M Dec 16 '19 at 08:44
1

I resolved it with a similar approach. Using either "? true : false" or "as bool" for contains. Although, curious why it wouldn't accept the result of contains method. As documentation says it should return a bool - https://api.flutter.dev/flutter/dart-core/Iterable/contains.html – GAMA Nov 02 '21 at 05:11

score 3 · Answer 2 · answered Jul 06 '20 at 08:42

I believe this will also work, still not sure why it doesn't return a bool though

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

score 0 · Answer 3 · answered Dec 15 '19 at 12:52

0

Where method returns a list, so you don't need to use toList(), and you should specify the return type of map method when you are using it.

  filter(_items) {
    return _items.map<String, List<bool>>((day, items) {
      return MapEntry(
        day, items.where((i) => i.stringProperty.contains(widget.filter)),
      );
    });
  }

answered Dec 15 '19 at 12:52

dshukertjr

15,244
11
57
94

shouldn't I return `>` instead of `>`? – Giacomo M Dec 15 '19 at 13:37
1

anyway I tried with both `bool` and `dynamic` but I still get the error. I am not even able to understand where this error occurs – Giacomo M Dec 15 '19 at 13:41

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

3 Answers3