From: Aaron Patterson <aaron@...>
Date: 2009-01-11T03:22:13+09:00
Subject: Re: Help with HTML parsing

On Sat, Jan 10, 2009 at 06:49:32PM +0900, Phlip wrote:
> Tom Morris wrote:
>
>> XPath that solves this:
>> contains(concat(' ', @class, ' '), ' w0 ')
>>
>> You can join multiple classes together like this:
>> contains(concat(' ', @class, ' '), ' w0 ') && contains(concat(' ',
>> @class, ' '), ' g ')
>>
>> It's not pretty. I've written it too much in my life.
>> I do wish XPath had a class selector.
>
> Noted. I'm writing an XPath DSL, above the level of a raw XML library, 
> and I just added to its pending feature list these line-items:
>
> #  TODO  :class => :symbol should do the trick contains(concat(' ', 
> @class, ' '), ' w0 ')
> #  TODO  :class => [] should do the trick contains(concat(' ', @class, ' 
> '), ' w0 ') && contains(concat(' ',@class, ' '), ' g ')
> #  TODO  :class => a string should be raw.
>
> Those won't fix low-level XPath, but they will be useful when my DSL 
> targets XHTML...

Couldn't you use CSS selectors when targeting XHTML (or XML even)?  In
Nokogiri, I have a CSS to XPath converter and just push the XPath down
to libxml.  For example:

  require 'nokogiri'
  
  doc = Nokogiri::HTML(<<-eoxml)
  <html>
    <body>
      <div class="one two">
        Hello
      </div>
    </body>
  </html>
  eoxml
  
  puts doc.at('.one.two').content

It also doesn't care if you're using XML or HTML.  The CSS selectors will get
converted to XPath either way.

-- 
Aaron Patterson
http://tenderlovemaking.com/