Just a overly simplified example of calling methods without arguments concurrently with Async and in parallel with Ractors

task.rb

require 'async'

module Task
  module_function

  def async(*method_names)
    Async do
      method_names.map do |job|
        Async do
          job.to_proc.call(self)
        end
      end
    end.result
  end

  def parallel(*method_names)
    method_names.map do |method_name|
      Ractor.new method_name do |name|
        name.to_proc.call(binding)
      end
    end
  end
end

##
# Just an example of calling methods without arguments
# concurrently with Async and in parallel with Ractors

def foo
  sleep 1
  puts 'foo'
end

def bar
  sleep 2
  puts 'bar'
end

Task.async(:foo, :foo, :bar).size
#>> foo
#>> foo
#>> bar
#=> 3

Task.parallel(:foo, :foo, :bar).size
#=> 3
#>> foo
#>> foo
#>> bar