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

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

License

The gem is available under the MIT License.