метод contains

bool contains(

)

override

Является ли value элементом множества.

final characters = <String>{'A', 'B', 'C'};
final containsB = characters.contains('B'); // true
final containsD = characters.contains('D'); // false

Реализация

bool contains(Object? element);

© 2012 the Dart project authors
Licensed under the BSD 3-Clause "New" or "Revised" License.
https://api.dart.dev/stable/2.18.5/dart-collection/SetMixin/contains.html