dartz_plus_generator 0.1.0

Code generator for dartz_plus AutoMapper.

Dartz Plus Generator

A code generator for dartz_plus that automatically creates mapping extensions between your data transfer objects (DTOs) and domain entities.

Features

• Automatic Mapper Generation: Generate bidirectional mapping extensions with a single annotation
• Type-Safe: Compile-time code generation ensures type safety
• Customizable: Control whether reverse mapping is generated
• Smart Field Resolution: Handles optional and nullable parameters intelligently
• Inheritance Support: Works with class hierarchies by collecting fields from superclasses

Installation

Add dartz_plus_generator as a dev dependency and dartz_plus as a regular dependency in your pubspec.yaml:

dependencies:
  dartz_plus: ^0.1.0

dev_dependencies:
  build_runner: ^2.10.4
  dartz_plus_generator: ^0.1.0

Then run:

flutter pub get

Usage

Basic Example

1. Annotate your DTO class with @Mapper and specify the target entity type:

import 'package:dartz_plus/dartz_plus.dart';

part 'user_model.g.dart'; // Include the generated file

@Mapper(UserEntity)
class UserDto {
  final String name;
  final int age;

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

class UserEntity {
  final String name;
  final int age;
  final String? email;

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

2. Run the code generator:

dart run build_runner build
# or for watch mode
dart run build_runner watch

3. The generator creates extension methods for mapping:

// Generated extension allows you to convert DTO to Entity
final dto = UserDto(name: 'John', age: 30);
final entity = dto.toUserEntity(); // UserEntity(name: 'John', age: 30)

// Reverse mapping is also generated by default
final backToDto = entity.toUserDto(); // UserDto(name: 'John', age: 30)

Controlling Reverse Mapping

By default, the generator creates bidirectional mappings. You can disable reverse mapping:

@Mapper(UserEntity, reverse: false)
class UserDto {
  // Only generates dto.toUserEntity()
  // No reverse entity.toUserDto() method
}

How It Works

The generator:

1. Analyzes the @Mapper annotation to identify the target type
2. Matches fields between source and target classes by name
3. Generates extension methods with to{TargetName}() methods
4. Handles optional and nullable parameters intelligently:
   • Required parameters must have matching fields in the source
   • Optional/nullable parameters are skipped if no matching field exists

Example with Optional Fields

@Mapper(ProfileEntity)
class ProfileDto {
  final String id;
  final String name;

  ProfileDto({required this.id, required this.name});
}

class ProfileEntity {
  final String id;
  final String name;
  final DateTime? createdAt; // Optional field

  ProfileEntity({
    required this.id,
    required this.name,
    this.createdAt,
  });
}

// Usage
final dto = ProfileDto(id: '123', name: 'Alice');
final entity = dto.toProfileEntity(); // createdAt will be null

Generated Code Example

For the basic example above, the generator produces:

// user_model.g.dart
part of 'user_model.dart';

extension UserDtoToUserEntityMapper on UserDto {
  UserEntity toUserEntity() {
    return UserEntity(
      name,
      age,
    );
  }
}

extension UserEntityToUserDtoMapper on UserEntity {
  UserDto toUserDto() {
    return UserDto(
      name: name,
      age: age,
    );
  }
}

Requirements

• Dart SDK: ^3.10.4
• dartz_plus: Compatible version
• build_runner: ^2.10.4 or higher

Build Configuration

The generator uses build.yaml for configuration. The default configuration:

builders:
  mapper:
    import: "package:dartz_plus_generator/builder.dart"
    builder_factories: ["mapperBuilder"]
    build_extensions: { ".dart": [".g.dart"] }
    auto_apply: dependents
    build_to: cache
    applies_builders: ["source_gen|combining_builder"]

Error Handling

The generator will throw helpful errors at build time if:

• @Mapper is applied to a non-class element
• Target type is not a class
• Target class doesn't have a default (unnamed) constructor
• Required parameters in the target constructor don't have matching fields in the source

Contributing

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

License

This project is licensed under the MIT License.

Links

• dartz_plus - The main functional programming library
• GitHub Repository