find subclasses

explicit.rb

class PullSource

  def self.implementations
    @implementations ||= {}
  end

  def self.register(name)
    implementations[name] << self
  end

end


class SomePullSource < PullSource

  register 'Some name'

end

<%= select_whatever PullSource.implementations.keys %>

implicit.rb

class PullSource

  def self.subclasses
    @subclasses ||= []
  end

  def self.inherited(sub)
    subclasses << sub
  end

end


class SomePullSource < PullSource



end