I am running list.firstWhere and this is sometimes throwing an exception:
Bad State: No element
When the exception was thrown, this was the stack:
#0 _ListBase&Object&ListMixin.firstWhere (dart:collection/list.dart:148:5)
I do not understand what this means an also could not identify the issue by looking at the source.
My firstWhere looks like this:
list.firstWhere((element) => a == b);
ベストアンサー1
This will happen when there is no matching element, i.e. when a == b is never true for any of the elements in list and the optional parameter orElse is not specified.
You can also specify orElse to handle the situation:
list.firstWhere((a) => a == b, orElse: () => print('No matching element.'));
If you want to return null instead when there is no match, you can also do that with orElse:
list.firstWhere((a) => a == b, orElse: () => null);
package:collection also contains a convenience extension method for the null case (which should also work better with null safety):
import 'package:collection/collection.dart';
list.firstWhereOrNull((element) => element == other);
See firstWhereOrNull for more information. Thanks to @EdwinLiu for pointing it out.