dart-model-from-json

name	dart-model-from-json
description	Generates Dart models from a JSON structure using json_annotation and equatable. Use this skill when the user provides a JSON object and wants the corresponding Dart model classes generated, or asks things like "generate a Dart model for this JSON", "create a model from this response", "dart model from json". Always use this skill when the user provides JSON and needs Dart model output.

Dart Model from JSON

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

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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.

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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

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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];
}

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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

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Naming Conventions

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

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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.

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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).

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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];
}