Свойство length
int lengthКоличество пар ключ-значение в словаре.
Исходный код
int get length => _map.length;
© 2012 the Dart project authors
Licensed under the Creative Commons Attribution-ShareAlike License v4.0.
https://api.dartlang.org/stable/1.24.3/dart-collection/MapView/length.html
