require 'black_magic'

class Demon
  attr_init(
    :name,
    :source,
  )
  .public(:name)
  .with_class_method_call(:summon)

  def summon
    puts "#{name} says 'bwoahahaha!'"
  end
end
demon = Demon.new(name: 'Lucy', source: 'fire')
demon.name
# => "Lucy"
demon.public_methods.include?(:source)
# => false
Demon.summon(name: 'Lucy', source: 'fire')
# Lucy says 'bwoahahaha!'
# => nil