How do you perform data transformation from JSON format to program objects?

In Flutter, methods like fromJson in data models are commonly used to convert data from JSON into program objects.

Example:

class User {
  final String name;
  final int age;

  User({required this.name, required this.age});

  factory User.fromJson(Map<String, dynamic> json) {
    return User(
      name: json['name'],
      age: json['age'],
    );
  }
}

// Usage:
final jsonString = '{"name": "Ivan", "age": 30}';
final Map<String, dynamic> userMap = jsonDecode(jsonString);
final user = User.fromJson(userMap);

Thus, first the JSON string is parsed into a Map using jsonDecode, then an object is created using the factory constructor fromJson. For complex models, packages like json_serializable can be used for automatic code generation.