dart-model-from-json

Dart Model from JSON

Generates Dart model classes from a JSON structure using json_annotation and equatable.

---

Input

The user provides a JSON object — either as a code block or pasted inline. If no JSON is provided, ask for it before proceeding.

---

Requirements

• Use json_annotation for JSON serialization
• Use equatable for value equality
• Include copyWith method
• Include fromJson and toJson methods
• Include props getter for equatable
• No @immutable decorator
• No documentation comments
• No @JsonKey annotations unless explicitly requested

---

Model Structure

import 'package:equatable/equatable.dart';
import 'package:json_annotation/json_annotation.dart';

part 'model_name.g.dart';

@JsonSerializable()
class ModelName extends Equatable {
  ModelName({
    required this.field1,
    this.field2,
    this.field3 = defaultValue,
  });

  final String field1;
  final int? field2;
  final bool field3;

  ModelName copyWith({
    String? field1,
    int? field2,
    bool? field3,
  }) {
    return ModelName(
      field1: field1 ?? this.field1,
      field2: field2 ?? this.field2,
      field3: field3 ?? this.field3,
    );
  }

  static ModelName fromJson(Map<String, dynamic> json) => _$ModelNameFromJson(json);
  Map<String, dynamic> toJson() => _$ModelNameToJson(this);

  @override
  List<Object?> get props => [field1, field2, field3];
}

---

Field Type Mapping

JSON type	Dart type
string	String
number (integer)	int
number (decimal)	double
boolean	bool
null or absent	nullable type (e.g., String?)
array of primitives	List<Type>
array of objects	List<ClassName>
object	separate class

---

Naming Conventions

• Class names: PascalCase
• Field names: camelCase
• Required fields: non-nullable with required keyword
• Optional fields: nullable with ?

---

Nested Object Rules

When to create separate classes

• Always create a class for objects with multiple properties
• Always create a class for array items that are objects
• Use List<String>, List<int>, etc. for primitive arrays — no class needed

Class name inference

Context	Class name
address field (object)	Address
profile.preferences (nested object)	Preferences
orders[] (array of objects)	Order
orders[].items[] (nested array)	OrderItem

If context is unclear, ask the user for the desired class name.

---

Output Format

Output each class as a separate code block labeled with the suggested filename:

user.dart

// ... User class

address.dart

// ... Address class

List all required classes in dependency order (leaf classes first, root last).

---

Example

Input JSON:

{
  "id": "123",
  "name": "John Doe",
  "age": 30,
  "isActive": true,
  "tags": ["tag1", "tag2"],
  "address": {
    "street": "123 Main St",
    "city": "New York",
    "zipCode": "10001"
  }
}

Output:

address.dart

import 'package:equatable/equatable.dart';
import 'package:json_annotation/json_annotation.dart';

part 'address.g.dart';

@JsonSerializable()
class Address extends Equatable {
  Address({
    required this.street,
    required this.city,
    required this.zipCode,
  });

  final String street;
  final String city;
  final String zipCode;

  Address copyWith({
    String? street,
    String? city,
    String? zipCode,
  }) {
    return Address(
      street: street ?? this.street,
      city: city ?? this.city,
      zipCode: zipCode ?? this.zipCode,
    );
  }

  static Address fromJson(Map<String, dynamic> json) => _$AddressFromJson(json);
  Map<String, dynamic> toJson() => _$AddressToJson(this);

  @override
  List<Object?> get props => [street, city, zipCode];
}

user.dart

import 'package:equatable/equatable.dart';
import 'package:json_annotation/json_annotation.dart';

import 'address.dart';

part 'user.g.dart';

@JsonSerializable()
class User extends Equatable {
  User({
    required this.id,
    required this.name,
    required this.age,
    required this.isActive,
    required this.tags,
    required this.address,
  });

  final String id;
  final String name;
  final int age;
  final bool isActive;
  final List<String> tags;
  final Address address;

  User copyWith({
    String? id,
    String? name,
    int? age,
    bool? isActive,
    List<String>? tags,
    Address? address,
  }) {
    return User(
      id: id ?? this.id,
      name: name ?? this.name,
      age: age ?? this.age,
      isActive: isActive ?? this.isActive,
      tags: tags ?? this.tags,
      address: address ?? this.address,
    );
  }

  static User fromJson(Map<String, dynamic> json) => _$UserFromJson(json);
  Map<String, dynamic> toJson() => _$UserToJson(this);

  @override
  List<Object?> get props => [id, name, age, isActive, tags, address];
}