Edit XML with Ruby

Question

I'm trying to edit an XML file and replace strings with ruby variables. For now this is my code :

<?xml version="1.0" encoding="US-ASCII"?>
<Standart-Profile>
    <class1>
        <class2>
            <class3>
               <value1>old_A</value2>
               <value1>old_B</value2>
               <value1>old_C</value2>
            </class3>
        </class2>
    </class1>
</Standart-Profile>

And this is the Ruby file :

require "rexml/text"
require 'rexml/document'
include REXML

def generate_2
    ...
end

def generate_1
    ...
end


File.open('Standart-Profile.xml') do |config_file|
  config = Document.new(config_file)
  config.root.elements['old_A'].text = 'generate_1'
  config.root.elements['old_B'].text = 'generate_2'
  config.root.elements['old_C'].text = 'generate_1'

  formatter = REXML::Formatters::Default.new
  File.open('New-Profile.xml', 'w') do |result|
  formatter.write(config, result)
  end
end

But I keep getting this error :

Final-Tool-Kit.rb:19:in `block in <main>': undefined method `text=' for nil:NilC
lass (NoMethodError)
        from test.rb:16:in `open'
        from test.rb:16:in `<main>'

Answer 1

Your problem is that you're looking for an element with the name old_A when you should be looking for an element with the text contents of old_A.

Here's a solution using Nokogiri, which I find more convenient than REXML:

require 'nokogiri' # gem install nokogiri

xml = "<Standart-Profile>
    <class1>
        <class2>
            <class3>
               <value1>old_A</value2>
               <value1>old_B</value2>
               <value1>old_C</value2>
            </class3>
        </class2>
    </class1>
</Standart-Profile>"

doc = Nokogiri.XML(xml)
doc.at('//text()[.="old_A"]').content = 'generate_1'
doc.at('//text()[.="old_B"]').content = 'generate_2'
doc.at('//text()[.="old_C"]').content = 'generate_3'

File.open('output.xml','w') do |f|
  f.puts doc
end
#=> <?xml version="1.0" encoding="US-ASCII"?>
#=> <Standart-Profile>
#=>     <class1>
#=>         <class2>
#=>             <class3>
#=>                <value1>generate_1</value1>
#=>                <value1>generate_2</value1>
#=>                <value1>generate_3</value1>
#=>             </class3>
#=>         </class2>
#=>     </class1>
#=> </Standart-Profile>

If you actually want to call a generate_1 method (as you have defined) then you would instead use:

...content = generate_1 # no quotes

Edit: Here's one way to do it with XPath in REXML (after I fixed the source XML to be valid):

require 'rexml/document'    
doc = REXML::Document.new(xml)
REXML::XPath.first(doc,'//*[text()="old_A"]').text = 'generate_1'
REXML::XPath.first(doc,'//*[text()="old_B"]').text = 'generate_2'
REXML::XPath.first(doc,'//*[text()="old_C"]').text = 'generate_3'
puts doc
#=> <Standart-Profile>
#=>     <class1>
#=>         <class2>
#=>             <class3>
#=>                <value1>generate_1</value1>
#=>                <value1>generate_2</value1>
#=>                <value1>generate_3</value1>
#=>             </class3>
#=>         </class2>
#=>     </class1>
#=> </Standart-Profile>