From: Phlip <phlip2005@...>
Date: 2008-08-13T03:47:37+09:00
Subject: Re: Hpricot and xpath

Li Chen wrote:

> I want to find the path to a tag I am interested using hpricot.
> According to the document and examples I think I should use #xpath
> method.
> 
> I expect that ruby will return the path as this:
> "/tag1/tag2/div[@id='header']"
> 
> but I get the following info:
> 
> tag1.rb:4: undefined method `xpath' for nil:NilClass (NoMethodError)
> 
> I wonder why method #xpath is not defined?

You gotta learn what those errors look like. If you have a 'nil' where you don't 
expect it, the error happens when you use the nil incorrectly, such as calling a 
method - like xpath - that nil does not have.

Your doc.at("header") returns nil.

> require 'hpricot'
> doc=Hpricot(open('tag.txt'))
> puts doc
> puts doc.at("header").xpath()

What does p doc.at('header') say? Would a .search (or equivalent) for '.header' 
work?

-- 
   Phlip
   http://www.oreillynet.com/onlamp/blog/2007/08/xpath_checker_and_assert_xpath.html