From: Phrogz <phrogz@...>
Date: 2008-01-13T14:39:58+09:00
Subject: Re: Stream Parsing with REXML

On Jan 12, 9:58 am, Marc Hoeppner <marc.hoepp...@molbio.su.se> wrote:
> Find the element "Gene-ref", allow me to access its children and then
> close and repeat for the next "Gene-ref entry. In xml code, that would
> look like
>
> <something here>
>  <Gene-ref>
>   <name>...</name>
>   <start>...</start>
>   <end>...</end>
>  </Gen-ref>
>  <Gen-ref>
>  ...

Here's a more targeted example, since I'm feeling helpful:

class Gene
  attr_accessor :name, :start, :end
  def initialize( name=nil, start=nil, endd=nil )
    @name  = name
    self.start = start
    self.end   = endd
  end
  def start=( start )
    @start = start.to_i
  end
  def end=( endd )
    @end = endd.to_i
  end
  def duration
    @end - @start
  end
  def to_s
    "<Gene '#{@name}' #{@start}-#{@end} (#{duration})> "
  end
end

class GeneParser
  GENE_TAG_NAME = "Gene-ref"
  def tag_start( name, attributes )
    case name
      when "root"
        # ignore
      when GENE_TAG_NAME
        @current_gene = Gene.new
      else
        @current_property = name
    end
  end

  def text( str )
    if @current_gene && @current_property
      @current_gene.send( @current_property.to_s + "=", str )
    end
  end

  def tag_end( name )
    if name == GENE_TAG_NAME
      puts @current_gene
      @current_gene = nil
    else
      @current_property = nil
    end
  end
end

require 'rexml/document'
REXML::Document.parse_stream( DATA, GeneParser.new )
#=> OUTPUT:
#=> <Gene 'foo' 17-42 (25)>
#=> <Gene 'bar' 43-50 (7)>

__END__
<root>
  <Gene-ref>
    <name>foo</name>
    <start>17</start>
    <end>42</end>
  </Gene-ref>
  <Gene-ref>
    <name>bar</name>
    <start>43</start>
    <end>50</end>
  </Gene-ref>
</root>