say i have
html/body/span/div/p/h1/i/font
html/body/span/div/div/div/div/table/tr/p/h1
html/body/span/p/h1/b
html/body/span/div
how can i get the common ancestor? in this case span would be the common ancestor of "font, h1, b, div" would be "span"
The function common_ancestor below does what you want.
require 'rubygems'
require 'nokogiri'
doc = Nokogiri::XML(DATA)
def common_ancestor *elements
return nil if elements.empty?
elements.map! do |e| [ e, [e] ] end #prepare array
elements.map! do |e| # build array of ancestors for each given element
e[1].unshift e[0] while e[0].respond_to?(:parent) and e[0] = e[0].parent
e[1]
end
# merge corresponding ancestors and find the last where all ancestors are the same
elements[0].zip(*elements[1..-1]).select { |e| e.uniq.length == 1 }.flatten.last
end
i = doc.xpath('//*[@id="i"]').first
div = doc.xpath('//*[@id="div"]').first
h1 = doc.xpath('//*[@id="h1"]').first
p common_ancestor i, div, h1 # => gives the p element
__END__
<html>
<body>
<span>
<p id="common-ancestor">
<div>
<p><h1><i id="i"></i></h1></p>
<div id="div"></div>
</div>
<p>
<h1 id="h1"></h1>
</p>
<div></div>
</p>
</span>
</body>
</html>
To find common ancestry between two nodes:
(node1.ancestors & node2.ancestors).first
A more generalized function that works with multiple nodes:
# accepts node objects or selector strings
class Nokogiri::XML::Element
def common_ancestor(*nodes)
nodes = nodes.map do |node|
String === node ? self.document.at(node) : node
end
nodes.inject(self.ancestors) do |common, node|
common & node.ancestors
end.first
end
end
# usage:
node1.common_ancestor(node2, '//foo/bar')
# => <ancestor node>