A new Flutter project.

git clone [this one]
flutter get

1. add annotation on class

   @JsonSerializable()
   class User {
     final int id;
     final String name;
     final String email;
     // ...
   }

2. pubspec.yaml, add package json_serializable

   dependencies:
     # ...others
     json_serializable: any

3. then fetch packages

   flutter pub get

4. add package build_runner to dev_dependencies

   dependencies:
     # ...others
     json_serializable: any
   
   dev_dependencies:
     # ...others
     build_runner:

5. then do this, it will generate a user.g.dart for you

   flutter pub run build_runner build

6. add methods

   part 'user.g.dart';
   @JsonSerializable()
   class User {
     factory User.fromJson(Map<String, dynamic> json) => _$UserFromJson(json);
   
     Map<String, dynamic> toJson() => _$UserToJson(this);
   
   

7. Now you don't need to extract and assign properties one by one from the JSON.