Typically we'd use hashes for this sort of things, but unlike hashes, going ChoiceTypes.doesnt_exist will raise an exception instead of returning nil.

gistfile1.rb

# Known poll types. Unknown types will raise
# an exception.
#
#   Poll::ChoiceTypes.time # => 'Choice::Time'
#
# @return [Struct]
ChoiceTypes = Struct.new(:time, :place, :text).new.tap do |types|
  types.time  = 'Choice::Time'
  types.place = 'Choice::Place'
  types.text  = 'Choice::Text'
end