Embed Ruby in xpath/Nokogiri - ruby

Question

Probably a pretty easy question:
I'm using Mechanize, Nokogori, and Xpath to parse through some html as such:
category = a.page.at("//li//a[text()='Test']")
Now, I want the term that I'm searching for in text()= to be dynamic...i.e. I want to create a local variable:
term = 'Test'
and embed that local ruby variable in the Xpath, if that makes sense.
Any ideas how?
My intuition was to treat this like string concatenation, but that doesn't work out:
term = 'Test'
category = a.page.at("//li//a[text()=" + term + "]")

Answer 1

When you use category = a.page.at("//li//a[text()=" + term + "]"). The final result to method is //li//a[text()=Test] where test is not in quotes. So to put quotes around string you need to use escape character \.
term = 'Test'
category = a.page.at("//li//a[text()=\"#{term}\"]")
or
category = a.page.at("//li//a[text()='" + term + "']")
or
category = a.page.at("//li//a[text()='#{term}']")
For example:
>> a="In quotes" #=> "In quotes"
>> puts "This string is \"#{a}\"" #=> This string is "In quotes"
>> puts "This string is '#{a}'" #=> This string is 'In quotes'
>> puts "This string is '"+a+"'" #=> This string is 'In quotes'

Answer 2

A little-used feature that might be relevant to your question is Nokogiri's ability to call a ruby callback while evaluating an XPath expression.
You can read more about this feature at http://nokogiri.org under the method docs for Node#xpath (http://nokogiri.org/Nokogiri/XML/Node.html#method-i-xpath), but here's an example addressing your question:
#! /usr/bin/env ruby
require 'nokogiri'
xml = <<-EOXML
<root>
<a n='1'>foo</a>
<a n='2'>bar</a>
<a n='3'>baz</a>
</root>
EOXML
doc = Nokogiri::XML xml
dynamic_query = Class.new do
def text_matching node_set, string
node_set.select { |node| node.inner_text == string }
end
end
puts doc.at_xpath("//a[text_matching(., 'bar')]", dynamic_query.new)
# => <a n="2">bar</a>
puts doc.at_xpath("//a[text_matching(., 'foo')]", dynamic_query.new)
# => <a n="1">foo</a>
HTH.