From: hurcan solter <hsolter@...>
Date: 2007-03-18T06:10:05+09:00
Subject: mixin classes (continuning from the last post)

Although I am a seasoned C/C++ programmer(+10 years), I am relatively
new to the ruby (about 2 days) despite having some reservations(ruby
debugger should be theslowest thing in the world) i am otherwise very
impressed with the language, I intend to use Ruby for some code
generation task ,Everything was going well until i hit that roadblock

class REXML::Element
    include TSort
    def initialize
        @dependencies=[]
    end
    def tsort_each_node(&block)
        @elements.each(&block)
    end
    def tsort_each_child(node, &block)
        @dependencies.each(&block) if @dependencies.size>0
    end
end
 well as you can see, i need to topologically sort some nodes in an
xml file and there was a module Tsort in the
ruby. from what understand i need to extend to class  REXML::Element
to feed Tsort algorithm. I have no problems
with adding the methods but when i feed this new node to tsort() I get
something like this

undefined method `size' for nil:NilClass
H:/ruby/somCompiler.rb:112:in `tsort_each_child'
c:/ruby/lib/ruby/1.8/tsort.rb:204:in
`each_strongly_connected_component_from
c:/ruby/lib/ruby/1.8/tsort.rb:183:in
`each_strongly_connected_component'
c:/ruby/lib/ruby/1.8/rexml/element.rb:939:in `each'
c:/ruby/lib/ruby/1.8/rexml/xpath.rb:53:in `each'
c:/ruby/lib/ruby/1.8/rexml/element.rb:939:in `each'
H:/ruby/somCompiler.rb:109:in `tsort_each_node'
.....
>From what I understand i am unable to add  @dependencies array to the
REXML::Element.Is it not possible
or i am missing something terribly here?
Any help would be greatly appreciated..
Hurcan