From: David Masover <ninja@...>
Date: 2008-05-30T00:45:27+09:00
Subject: Re: Surprising Extend

On Thursday 29 May 2008 10:36:27 Leslie Viljoen wrote:
> >
> > Can you show some real code and real error messages?  Normally there
> > should not be an issue with your first approach.
> ----In StringExt.rb:
> 
> module StringExt
> 	def to_hex
> 		unpack("C*").map{|b| b.to_s(16)}.join(" ")
> 	end
> end
> 
> ----In use.rb:
> 
> require 'StringExt'
> 
> String.extend StringExt
> s = "anystringwilldo"
> puts s.to_hex

I'm not sure, but considering that you can extend individual instances, that 
method has probably become a class method for String? As in, String.to_hex?

But your _first_ approach should work. In StringExt.rb:

class String
  def to_hex
    unpack("C*").map{|b| b.to_s(16)}.join(" ")
  end
end

In use.rb:

require 'StringExt'
s = 'anystringwilldo'
puts s.to_hex

For me, running use.rb outputs

61 6e 79 73 74 72 69 6e 67 77 69 6c 6c 64 6f

tested in both Ruby 1.8 and Ruby 1.9.