Generating dart file with json_serializable package - dart

Question

According to the json_serializable package installing instructions, you should add the following dependency:
dependencies:
json_serializable: ^2.0.3
This is my code:
import 'package:json_annotation/json_annotation.dart';
part 'person.g.dart';
#JsonSerializable(nullable: false)
class Person {
final String firstName;
final String lastName;
final DateTime dateOfBirth;
Person({this.firstName, this.lastName, this.dateOfBirth});
factory Person.fromJson(Map<String, dynamic> json) => _$PersonFromJson(json);
Map<String, dynamic> toJson() => _$PersonToJson(this);
}
Now running this in Flutter:
flutter packages pub run build_runner build
Or this for a Dart project:
pub run build_runner build
I get the following error:
Could not find package "build_runner". Did you forget to add a dependency?
What's wrong?

Answer 1

This is a problem with how Pub is set up to automatically generate the installation instructions. Here are the dependencies that you actually need to add:
dependencies:
json_annotation: ^2.0.0
dev_dependencies:
build_runner: ^1.0.0
json_serializable: ^2.0.0
This is shown in the json_serializable example.
Now you can generate the dart file for a class like this
import 'package:json_annotation/json_annotation.dart';
part 'person.g.dart';
#JsonSerializable(nullable: false)
class Person {
final String firstName;
final String lastName;
final DateTime dateOfBirth;
Person({this.firstName, this.lastName, this.dateOfBirth});
factory Person.fromJson(Map<String, dynamic> json) => _$PersonFromJson(json);
Map<String, dynamic> toJson() => _$PersonToJson(this);
}
by running this in a Flutter project:
flutter packages pub run build_runner build
or this in a Dart project:
pub run build_runner build
Other notes:
Make sure that part 'person.g.dart' matches the name of your person.dart model class file. That is, don't call it example.g.dart.

Answer 2

you need to run
flutter packages get
first