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Nokogiri: choose content between elements A and B

What is the smartest way for Nokogiri to select all the content between the start and stop element (including the start / stop element)?

Check out the sample code below to see what I'm looking for:

require 'rubygems' require 'nokogiri' value = Nokogiri::HTML.parse(<<-HTML_END) "<html> <body> <p id='para-1'>A</p> <div class='block' id='X1'> <p class="this">Foo</p> <p id='para-2'>B</p> </div> <p id='para-3'>C</p> <p class="that">Bar</p> <p id='para-4'>D</p> <p id='para-5'>E</p> <div class='block' id='X2'> <p id='para-6'>F</p> </div> <p id='para-7'>F</p> <p id='para-8'>G</p> </body> </html>" HTML_END parent = value.css('body').first # START element @start_element = parent.at('p#para-3') # STOP element @end_element = parent.at('p#para-7')

The result (return value) should look like this :

 <p id='para-3'>C</p> <p class="that">Bar</p> <p id='para-4'>D</p> <p id='para-5'>E</p> <div class='block' id='X2'> <p id='para-6'>F</p> </div> <p id='para-7'>F</p>

Update: This is my current solution, although I think there should be something smarter:

 @my_content = "" @selected_node = true def collect_content(_start) if _start == @end_element @my_content << _start.to_html @selected_node = false end if @selected_node == true @my_content << _start.to_html collect_content(_start.next) end end collect_content(@start_element) puts @my_content
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3 answers

The path is too smart oneliner that uses recursion:

 def collect_between(first, last) first == last ? [first] : [first, *collect_between(first.next, last)] end

Iterative solution:

 def collect_between(first, last) result = [first] until first == last first = first.next result << first end result end

EDIT: (short) asterisk explanation

It is called the splat operator. It "expands" the array:

 array = [3, 2, 1] [4, array] # => [4, [3, 2, 1]] [4, *array] # => [4, 3, 2, 1] some_method(array) # => some_method([3, 2, 1]) some_method(*array) # => some_method(3, 2, 1) def other_method(*array); array; end other_method(1, 2, 3) # => [1, 2, 3]
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 # monkeypatches for Nokogiri::NodeSet # note: versions of these functions will be in Nokogiri 1.3 class Nokogiri::XML::NodeSet unless method_defined?(:index) def index(node) each_with_index { |member, j| return j if member == node } end end unless method_defined?(:slice) def slice(start, length) new_set = Nokogiri::XML::NodeSet.new(self.document) length.times { |offset| new_set << self[start + offset] } new_set end end end # # solution #1: picking elements out of node children # NOTE that this will also include whitespacy text nodes between the <p> elements. # possible_matches = parent.children start_index = possible_matches.index(@start_element) stop_index = possible_matches.index(@end_element) answer_1 = possible_matches.slice(start_index, stop_index - start_index + 1) # # solution #2: picking elements out of a NodeSet # this will only include elements, not text nodes. # possible_matches = value.xpath("//body/*") start_index = possible_matches.index(@start_element) stop_index = possible_matches.index(@end_element) answer_2 = possible_matches.slice(start_index, stop_index - start_index + 1)
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For completeness, XPath solution only :)
It creates the intersection of two sets, the next siblings of the starting element and the previous siblings of the final element.

Basically, you can build an intersection with:

  $a[count(.|$b) = count($b)]

A small separation of variables for readability:

 @start_element = "//p[@id='para-3']" @end_element = "//p[@id='para-7']" @set_a = "#@start_element/following-sibling::*" @set_b = "#@end_element/preceding-sibling::*" @my_content = value.xpath("#@set_a[ count(.|#@set_b) = count(#@set_b) ] | #@start_element | #@end_element")

Brothers and sisters do not include the element itself, so the source and destination elements must be included in the expression separately.

Edit: Simple solution:

 @start_element = "p[@id='para-3']" @end_element = "p[@id='para-7']" @my_content = value.xpath("//*[preceding-sibling::#@start_element and following-sibling::#@end_element] | //#@start_element | //#@end_element")
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