The Buckblog

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:

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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:

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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:

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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.