Dart to JSON Copy Constructor

main.dart

class Person {
  String name;
  int age;

  Person({this.name, this.age});

  Person copyWithUpdate({
    String name,
    int age,
  }) {
    return Person(
      name: name ?? this.name,
      age: age ?? this.age,
    );
  }

  Person.fromJson(Map<String, dynamic> json) {
    name = json['name'];
    age = json['age'];
  }

  Map<String, dynamic> toJson() {
    final Map<String, dynamic> data = new Map<String, dynamic>();
    data['name'] = this.name;
    data['age'] = this.age;
    return data;
  }
  
  String toString() {
    return "Person: $name $age";
  }
}

void main() {
  Person a = Person(name: "Alpha", age: 20);
  Person b = a.copyWithUpdate(name: "Beta");
  print(a);
  print(b);
}