Dartlero – a simple domain model framework

We will now discuss Dartlero to get an idea of what a domain model framework is all about and how you can build upon it. Dartlero is a limited model framework used in teaching and learning basic data structures in Dart. Get your copy of Dartlero from Pub or from GitHub with the following command:

git clone git://github.com/dzenanr/dartlero.git 

Open the dartlero folder in your Dart Editor. Dartlero's code sits in the lib folder and the library file dartlero.dart, referencing three part files in the model subdirectory (lines (3) to (5)):

library dartlero;
import 'package:unittest/unittest.dart';

part 'model/concept_model.dart';                              (3)
part 'model/concept_entities.dart';                           (4)
part 'model/concept_errors.dart';                             (5)

Dartlero is just a library; it cannot be started by itself. We see that the central concepts are entities and...