Ruby: How to find XML child element from specific element using xpath? - ruby

Question

Given xml
<a>
<b key=1>
<c value=xxx />
</b>
<b key=2>
<c value=yyy />
</b>
</a>
Goal: Get each "b" first, then get the "c" under that "b", like result below. With XPath for searching child.
for <b key=1>
<c value=xxx />
for <b key=2>
<c value=xxx />
but below code
b_elements = XPath.match(xml, "//b[#key]")
b_elements.each do |b_element|
puts b_element.elements["//c"]
end
will result in yeilding
for <b key=1>
<c value=xxx />
<c value=yyy />
for <b key=2>
<c value=xxx />
<c value=yyy />
instead of just getting the "c" under each "b"
I had tried below method but no luck, seems that if using Xpath, it will automatically search from root element
b.get_elements("//c")
XPath.first(b, "//c")
My workaround now is traverse child element 1 layer at a time and search for desired key, which seems quite stupid comparing to using XPath.
Please advise, thanks : )
Reference:
http://ruby-doc.org/stdlib-1.9.3/libdoc/rexml/rdoc/REXML/Element.html#method-i-each_element_with_attribute

Answer 1

Not sure here, but my assumption is that XPath looks at the first char, sees that it is a /, and thinks that the path is absolute (because the path starting with / is meant to be absolute).
Probably you can force the path to be relative by using a . before //, so the parser doesn't confuse // for /?
I mean, instead of "//c" use ".//c"? Hope this helps.