Callable

Callable is a minimal Ruby mix-in that provides your classes with a simple .call class method (plus to_proc). It allows you to instantiate and immediately invoke an instance method (call) without boilerplate or additional dependencies. Perfect for clean, readable, and concise service objects.

Learn more at https://rubydoc.info/gems/callable-mixin

Features

• Provides a .call class method to any Ruby class.
• Supports Class#to_proc, letting you use &YourService in Enumerable methods.
• Transparently forwards positional args, keyword args, and blocks to #call.
• Raises ConstructionError (subclass of ArgumentError) for constructor arity/kwarg mismatches.
• Raises NotImplementedError when the class does not define an instance #call.
• Zero external runtime dependencies.
• Compatible with MRI Ruby 2.3 through Ruby 3.x.

Installation

Add this to your application's Gemfile (version 0.2.0 or later):

gem 'callable-mixin', '~> 0.2.0'

Then execute:

bundle install

Or install directly:

gem install callable-mixin

Usage

Example Service with Multiple Arguments

class SendNotification
  include Callable

  def initialize(user, message)
    @user = user
    @message = message
  end

  def call
    NotificationMailer.notify(@user, @message).deliver_now
  end
end

• Explicit invocation when you need multiple constructor args:

  users.each do |user|
    SendNotification.call(user, "Your message here")
  end
  
  # You can also call via the `.()` alias:
  SendNotification.(user, "Your message here")

Example Service with Single Argument (to_proc Shorthand)

class WelcomeUser
  include Callable

  def initialize(user)
    @user = user
  end

  def call
    NotificationMailer.welcome(@user).deliver_now
  end
end

• Proc shorthand for one-arg services:

  users.each(&WelcomeUser)
  
  # Or invoke with the `.()` alias:
  WelcomeUser.(current_user)

Using in a Plain Ruby Script

require 'callable-mixin'

# Define your service with Callable
class MyService
  include Callable

  def initialize(value)
    @value = value
  end

  def call
    puts "Processing #{@value}"
  end
end

# Invoke the service
MyService.call("some data")

# Or use the `.()` alias:
MyService.("more data")

Development

After cloning the repo, install dependencies with bundle install, then run tests with bundle exec rspec.

Contributing

Please follow these resources before submitting code or issues:

• Code of Conduct
• Contributing Guide
• Pull Request Template

Bug reports and pull requests are welcome on GitHub: https://github.com/dbongo/callable-mixin

License

The gem is available under the MIT License.