example_service.rb

# to be called:
# ExampleService[1, {some: 'opt'}]
class ExampleService < Services::Base
  # customize your setup
  def initialize(concrete, arguments = {})
    @concrete  = concrete
    @arguments = arguments
  end
  
  # customize your processing
  def call
  end
end

services_base.rb

module Services
  class Base
    class << self
      def call
        new(*args).call
      end
      alias_method :[], :call
    end
    
    private_class_method :new
    
    # to be customized on subclases
    def call
      raise NotImplementedError
    end
  end
end