From: Ryan Leavengood <mrcode@...>
Date: 2005-05-02T03:46:58+09:00
Subject: Re: parsing xml documents using rexml

Derek wrote:
> Hi,
> 
> I'm new to ruby.
> I want to use ruby to process an xml file. 
> 
> At the moment I am using the REXML but are open to other xml parsers.
> 
> In the xml file below how would I go about processing the section <details> in the following way: -
>  - when the tag <copy> is detected perform a method "copy". within the "copy" method extract other child tags within the current <copy> element.
>  - when the tag <mkdir> is detected perform a method "mkdir". within the "mkdir" method extract other tags within the current <mkdir> element.
> 
> I've looked at using XPATH, and have been able to extract specific information but have not worked out how to do it.

Here is a somewhat sloppy version, but it works:

CODE_BEGIN
require 'rexml/document'
include REXML

def copy(source, target)
   puts "Copying from #{source} to #{target}"
end

def mkdir(dir)
   puts "Making directory #{dir}"
end

xml_file = ARGV[0] || 'filegroup.xml'
doc = Document.new File.new(xml_file)
doc.elements.each('fileGroup/details') do |element|
   element.each do |command|
     if command.kind_of? Element
       case command.name
       when 'copy'
         source = ''
         target = ''
         command.each do |param|
           if param.kind_of? Element
             if param.name == 'source'
               source = param.text
             elsif param.name == 'target'
               target = param.text
             end
           end
         end
         copy(source, target)
       when 'mkdir'
         mkdir(command.text)
       else
         puts "Unknown command: #{command.name}"
       end
     end
   end
end
CODE_END

If you used attributes instead of subtags it would be easier:
<copy source="something" target="whatever"/>
<mkdir dir="some_dir"/>

CODE_BEGIN
doc.elements.each('fileGroup/details') do |element|
   element.each do |command|
     if command.kind_of? Element
       case command.name
       when 'copy'
         copy(command.attributes['source'], command.attributes['target'])
       when 'mkdir'
         mkdir(command.attributes['dir'])
       else
         puts "Unknown command: #{command.name}"
       end
     end
   end
end
CODE_END

Ryan Leavengood