This post originated from an RSS feed registered with Ruby Buzz by Jamis Buck. Original Post: Enumerated types in Ruby Feed Title: the buckblogs here Feed URL: http://weblog.jamisbuck.org/blog.cgi/programming/index.rss Feed Description: Jamis Buck's corner of the blogging universe. Mostly about ruby, but includes ramblings on a variety of topics. Latest Ruby Buzz Posts Latest Ruby Buzz Posts by Jamis Buck Latest Posts From the buckblogs here

It’s not often that I need an enumerated type in Ruby—there is usually a more elegant way of doing things, I’ve found. But when I’m interfacing with a C library (such as fmod, in this case), it can be a pain to stop and define constants for every enumerated type.

It’s probably been done before, but I found the following little class quite helpful:

  class EnumeratedType
    class <<self
      def start(n)
        @next_value = n
      end

      def const_missing(sym)
        @next_value ||= 0
        const_set(sym, @next_value)
        @next_value += 1
      end
    end
  end

It lets you create enumerated types like this:

  class OutputType < EnumeratedType
    AUTODETECT
    UNKNOWN
    NOSOUND
    WAVWRITER
    DSOUND
    WINMM
    ASIO
    OSS
    ALSA
    ESD
    SOUNDMANAGER
    COREAUDIO
    XBOX
    PS2
    GC
    XBOX360
    PSP
  end

If you want to start with a different integer than 0, you can just do:

class OutputType < EnumeratedType
  start 15
  AUTODETECT
  ...
end

You can also use start anywhere in the list, to have subsequent constants enumerated starting with the given value.