Type error when adding two derivatives of same base class in a List

user_7128933 0
Viewed 84

I have this code:

List<Widget> _elementsHere = _locationsRegister
        .map((e) => ShowingLocation(
              num: e.num,
              name: e.name,
              icon: e.icon,
            ))
        .toList();

I have specified List<Widget>, but if I print _elementsHere.runtimeType.toString() in console, I can see List<ShowingLocation>. In fact if I add this code:

_elementsHere.insert(0, Text('hello'));

I receive error that Text isn't a subtype of ShowingLocation, despite it's a Widget.

I want _elementsHere as List<Widget> instead of List<ShowingLocation>.

dart casting
2 Answers

This can be solved by specifying the object type in the generics field of the map function. Since you're not specifying the type, it's being assumed to be an iterable of ShowingLocation.

Do this instead:

List<Widget> _elementsHere = _locationsRegister
        .map<Widget>((e) => ShowingLocation(
              num: e.num,
              name: e.name,
              icon: e.icon,
            ))
        .toList();
user_132501420

Another option is as keyword.

List<Widget> _elementsHere = _locationsRegister
    .map((e) => (ShowingLocation(
          num: e.num,
          name: e.name,
          icon: e.icon,
        ) as Widget))
    .toList();
user_73142110
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