Introducing a mixin class that implements a toJsonDelta() method that serializes the object to a JSON map of values of the changes in the object.

Usage

final person = Person("John", "Doe", 30);
person.lastName = "Smith";
person.age = 31;
final delta = person.toJsonDelta(); // {"lastName": "Smith", "age": 31}

Implement in your models

An important note is that you call the saveJsonDeltaState() in the model's constructor to set an initial state to compare against later.

class Person extends JsonSerializable with JsonDelta {
  String firstName;
  String lastName;
  int age;

  Person({
    required this.firstName,
    required this.lastName,
    required this.age,
  }) {
    // Save the initial state of your object in the constructor
    saveJsonDeltaState();
  }

  @override
  Map<String, dynamic> toJson() {
    return {
      'firstName': firstName,
      'lastName': lastName,
      'age': age,
    };
  }
}

Additional information

This package is compatible with json_serializable which facilitates your generation of JSON.