retainWhere method
Removes all elements of this set that fail to satisfy test
.
final characters = <String>{'A', 'B', 'C'};
characters.retainWhere(
(element) => element.startsWith('B') || element.startsWith('C'));
print(characters); // {B, C}
Implementation
void retainWhere(bool test(E element)) =>
update((_) => value.removeWhere(test));