Json to dart beans are provided, and dart files ending in entity are provided to generate dart bean factory for use.

Right click on package -> New -> Json To DartMappable　And Then you will know how to use.

If you change the fields in the class, right click on package -> Flutter Command -> Flutter Run Build Runner, shortcut key is changed to Alt + r.

Don't forget to set up dart_mappable into your project : https://pub.dev/packages/dart_mappable
Add into your pubspec.yaml

dependencies:
  dart_mappable: ^3.0.0  
dev_dependencies: 
  build_runner: ^2.1.0
  dart_mappable_builder: ^3.0.2

Or Run Terminal

flutter pub add dart_mappable
flutter pub add build_runner --dev
flutter pub add dart_mappable_builder --dev