From: Robert McGovern <tarasis@...>
Date: 2002-12-20T06:37:34+09:00
Subject: Re: determing defined constants for a class

> A class is-a module (i.e. the "Class" class is derived from the "Module" 
> class). So to determine the constants for a class just call 
> Class#constants.

*sigh* Thanks Lyle, that was a Doh! moment.

I had tried doing self.constants and had it not work, checked the docs 
and then posted the question.

Okay so constants returns an array of the constant names as a string in 
short form (i.e. not including the path needed to use them). Hmm, so 
with the following sample code, if I want to verify that an method is 
passed a valid constant argument what would I want to do? (given the 
constant will be passed into the method as a numeric)

example:

module ID3
     module V2
	class Frame
	    #constants
	    TRACK_LENGTH = 0
	    TRACK_TITLE = 1
	    # .... and so on

     	    @frame_id = nil # this objects frame id

     	    def frame_id=(f_id)
	        @frame_id = f_id if ID3::V2::Frame.constants.include? (f_id)
	end # frame
     end # v2
end # id3

frame = ID3::V2::Frame.new
# the following will fail because the constants returned
# are in short from i.e. TRACK_LENGTH and f_id in the method is 0
f.frame_id = ID3::V2::Frame::TRACK_LENGTH

Rob



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