Ruby #handles? style factories

elsewhere.rb

Superclass.for(obj) # => The concrete subclass instance you wanted

registered.rb

module Registered
  def for(target)
    registry.find {|candidate| candidate.handles?(target) }
      .new(target)
  end

  def registry
    @@registry ||= [] # rubocop:disable Style/ClassVars
  end

  def register(candidate)
    registry.unshift(candidate)
  end

  def handles?(_target)
    true
  end
end

subclass.rb

require "superclass"

class Subclass < Superclass
  register(self)
  
  def self.handles(target)
    # return a boolean
  end
end
 

superclass.rb

require "registered"

class Superclass
  extend Registered
  register(self) # Because this will always be evaluated first, it serves as a default.
end