Easy CopyWith

A lightweight Dart package for automatic generation of copyWith methods using the @CopyWith annotation.

Features

🚀 Simple annotation-based API
⚡ Build-time code generation (no runtime overhead)
🔄 Supports nullable and non-nullable fields
🎯 Compatible with freezed patterns
📦 Minimal dependencies
🛠️ Easy integration with existing projects

Installation

Add to your pubspec.yaml:

dependencies:
  easy_copy_with: ^1.0.0

dev_dependencies:
  build_runner: ^2.3.3

Then run:

dart pub get

Quick Start

Import the package:

import 'package:easy_copy_with/easy_copy_with.dart';

Add part directive:

part 'your_file.copy_with.g.dart';

Annotate your class:

@CopyWith()
class Person {
  final String name;
  final int age;
  final String? email;

  const Person({
    required this.name,
    required this.age,
    this.email,
  });
}

Generate code:

dart run build_runner build

Use the generated copyWith method:

final person = Person(name: 'John', age: 30);
final olderPerson = person.copyWith(age: 31);

Example

import 'package:easy_copy_with/easy_copy_with.dart';

part 'user.copy_with.g.dart';

@CopyWith()
class User {
  final String name;
  final int age;
  final String? email;
  final bool isActive;

  const User({
    required this.name,
    required this.age,
    this.email,
    this.isActive = true,
  });
}

void main() {
  final user = User(name: 'Alice', age: 25);

  // Create copy with single field change
  final updatedUser = user.copyWith(age: 26);

  // Create copy with multiple field changes
  final activeUser = user.copyWith(
    email: 'alice@example.com',
    isActive: true,
  );

  print('Original: ${user.name}, ${user.age}');
  print('Updated: ${updatedUser.name}, ${updatedUser.age}');
}

Generated Code

The package uses source_gen and build_runner to analyze classes with the @CopyWith annotation and generate extension methods at build time.

For the example above, the generated code looks like:

extension UserCopyWith on User {
  User copyWith({
    String? name,
    int? age,
    String? email,
    bool? isActive,
  }) {
    return User(
      name: name ?? this.name,
      age: age ?? this.age,
      email: email ?? this.email,
      isActive: isActive ?? this.isActive,
    );
  }
}

Commands

# Generate code once
dart run build_runner build

# Watch for changes and rebuild automatically
dart run build_runner watch

# Clean generated files
dart run build_runner clean

Requirements

Dart SDK: >=3.9.2
Compatible with Flutter projects

Contributing

Contributions are welcome! Please feel free to submit a Pull Request.

License

This project is licensed under the BSD 3-Clause License - see the LICENSE file for details.