How do I create XML using Nokogiri::XML::Builder with a hyphen in the element name?

I am trying to build an XML document using Nokogiri. Some of the elements have hyphens in them. Here's an example:

require "nokogiri"
builder = Nokogiri::XML::Builder.new do |xml|
  xml.foo_bar "hello"
end

puts builder.to_xml

Which produces:

<?xml version="1.0"?>
<f开发者_高级运维oo_bar>hello</foo_bar>

However, when I try:

builder = Nokogiri::XML::Builder.new do |xml|
  xml.foo-bar "hello"
end

I get:

syntax error, unexpected tSTRING_BEG, expecting kDO or '{' or '('
  xml.foo-bar "hello"

Now I realise this is because the hyphen is being interpreted as foo MINUS bar.

How should I do this?

Here you go:

require 'nokogiri'

b = Nokogiri::XML::Builder.new do |xml|
  xml.send(:"fooo-bar", "hello")
end

puts b.to_xml

Bart Vandendriessche's answer works but there is a simpler solution if you only want a text field within the element.

require 'nokogiri'

b = Nokogiri::XML::Builder.new do |xml|
  xml.send(:"foo-bar", 'hello')
end

puts b.to_xml

Generates:

<?xml version="1.0"?>
<foo-bar>hello</foo-bar>

If you need them to be nested then you can pass a block

require 'nokogiri'

b = Nokogiri::XML::Builder.new do |xml|
  xml.send(:'foo-bar') {
    xml.send(:'bar-foo', 'hello')
  }
end

puts b.to_xml

Generates:

<?xml version="1.0"?>
<foo-bar>
  <bar-foo>hello</bar-foo>
</foo-bar>

Aaron Patterson's answer is correct and will work for element names containing any character that may otherwise be interpreted by the Ruby parser.

Answering Angela's question: to place text inside a element created this way you can do something like this:

require 'rubygems'
require 'nokogiri'

b = Nokogiri::XML::Builder.new do |xml|
  xml.send(:'foo.bar') {
    xml.text 'hello'
  }
end

puts b.to_xml