How can I extract the node names for fragmented XML document using Ruby? - ruby

Question

I an XML-like document which is pre-processed by a system out of my control. The format of the document is like this:
<template>
Hello, there <RECALL>first_name</RECALL>. Thanks for giving me your email.
<SETPROFILE><NAME>email</NAME><VALUE><star/></VALUE></SETPROFILE>. I have just sent you something.
</template>
However, I only get as a text string what is between the <template> tags.
I would like to be able to extract without specifying the tags ahead of time when parsing. I can do this with the Crack gem but only if the tags are at the end of the string and there is only one.
With Crack, I can put a string like
string = "<SETPROFILE><NAME>email</NAME><VALUE>go#go.com</VALUE></SETPROFILE>"
and my output from Crack is:
{"SETPROFILE"=>{"NAME"=>"email", "VALUE"=>"go#go.com"}}
Then I can use a case statement for the possible values I care about.
Given that I need to have multiple <tags> in the string and they cannot be at the end of the string, how can I parse out the node names and the values easily, similar to what I do with crack?
These tags also need to be removed. I would like to continue to use the excellent suggestion from #TinMan.
It works perfectly once I know the name of the tag. The number of tags will be finite. I send the tag to the appropriate method once I know it, but it needs to get parsed out easily first.

Answer 1

Using Nokogiri, you can treat the string as a DocumentFragment, then find the embedded nodes:
require 'nokogiri'
doc = Nokogiri::XML::DocumentFragment.parse(<<EOT)
Hello, there <RECALL>first_name</RECALL>. Thanks for giving me your email.
<SETPROFILE><NAME>email</NAME><VALUE><star/></VALUE></SETPROFILE>. I have just sent you something.
EOT
nodes = doc.search('*').each_with_object({}){ |n, h|
h[n] = n.text
}
nodes # => {#<Nokogiri::XML::Element:0x3ff96083b744 name="RECALL" children=[#<Nokogiri::XML::Text:0x3ff96083a09c "first_name">]>=>"first_name", #<Nokogiri::XML::Element:0x3ff96083b5c8 name="SETPROFILE" children=[#<Nokogiri::XML::Element:0x3ff96083a678 name="NAME" children=[#<Nokogiri::XML::Text:0x3ff960836884 "email">]>, #<Nokogiri::XML::Element:0x3ff96083a650 name="VALUE" children=[#<Nokogiri::XML::Element:0x3ff96083a5c4 name="star">]>]>=>"email", #<Nokogiri::XML::Element:0x3ff96083a678 name="NAME" children=[#<Nokogiri::XML::Text:0x3ff960836884 "email">]>=>"email", #<Nokogiri::XML::Element:0x3ff96083a650 name="VALUE" children=[#<Nokogiri::XML::Element:0x3ff96083a5c4 name="star">]>=>"", #<Nokogiri::XML::Element:0x3ff96083a5c4 name="star">=>""}
Or, more legibly:
nodes = doc.search('*').each_with_object({}){ |n, h|
h[n.name] = n.text
}
nodes # => {"RECALL"=>"first_name", "SETPROFILE"=>"email", "NAME"=>"email", "VALUE"=>"", "star"=>""}
Getting the content of a particular tag is easy then:
nodes['RECALL'] # => "first_name"
Iterating over all the tags is also easy:
nodes.keys.each do |k|
...
end
You can even replace a tag and its content with text:
doc.at('RECALL').replace('Fred')
doc.to_xml # => "Hello, there Fred. Thanks for giving me your email. \n<SETPROFILE>\n <NAME>email</NAME>\n <VALUE>\n <star/>\n </VALUE>\n</SETPROFILE>. I have just sent you something.\n"
How to replace the nested tags is left to you as an exercise.