auto_decorator

Convention-based decorator autoloading for Rails models.

Decorators are plain Ruby modules that get automatically included into your model classes based on file naming convention — no configuration required.

Why not Draper? Draper wraps objects in presenter classes. auto_decorator adds methods directly to the model. Less indirection, less boilerplate, same result for most use cases.

Installation

Add to your Gemfile:

gem "auto_decorator"

Usage

Convention

Place decorator files in app/decorators/. The gem discovers them automatically and includes each module into the matching model class:

File	Module	Included into
app/decorators/user_decorator.rb	UserDecorator	User
app/decorators/organization_decorator.rb	OrganizationDecorator	Organization
app/decorators/organizations/employee_decorator.rb	Organizations::EmployeeDecorator	Organizations::Employee

Example

# app/decorators/user_decorator.rb
module UserDecorator
  def full_name
    [first_name, last_name].compact.join(" ")
  end

  def to_s
    full_name.presence || email
  end
end

# app/decorators/organizations/employee_decorator.rb
module Organizations
  module EmployeeDecorator
    def active?
      status == "active"
    end
  end
end

Since the modules are included directly into the model, decorated methods are available anywhere the model is used:

user = User.find(1)
user.full_name  # => "Alice Smith"
user.to_s       # => "Alice Smith"

Generator

Scaffold a new decorator with:

rails g decorator User
# → creates app/decorators/user_decorator.rb

rails g decorator Organizations::Employee
# → creates app/decorators/organizations/employee_decorator.rb

Generated file for User:

# frozen_string_literal: true

module UserDecorator
end

Generated file for Organizations::Employee:

# frozen_string_literal: true

module Organizations
  module EmployeeDecorator
  end
end

Configuration

The gem works with zero configuration. To override defaults:

# config/initializers/auto_decorator.rb
AutoDecorator.configure do |config|
  config.decorators_path = "app/decorators"  # relative to Rails.root
  config.decorator_suffix = "Decorator"
end

How it works

On every config.to_prepare (triggered on boot and in development on each request):

1. Glob all *_decorator.rb files under decorators_path
2. Derive the module name from the file path: organizations/employee_decorator.rb → Organizations::EmployeeDecorator
3. Derive the model name by stripping the suffix: Organizations::EmployeeDecorator → Organizations::Employee
4. Call ModelClass.include(DecoratorModule) — skips if already included

If the model class doesn't exist (e.g. a decorator for a non-existent model), it is silently skipped.

Compatibility

| | | | ----- | --------- | | Ruby | ≥ 3.2 | | Rails | 7.0 – 8.1 |

Contributing

Bug reports and pull requests are welcome on GitHub.

License

MIT