Converting nested hash into XML using nokogiri

Question

I have many levels of nested hash like:

 { :foo => 'bar', :foo1 => { :foo2 => 'bar2', :foo3 => 'bar3', :foo4 => { :foo5 => 'bar5' }}}

How can I convert them into an XML like this?:

<foo>bar</foo>
<foo1>
    <foo2>bar2</foo2>
    <foo3>bar3</foo3>
    <foo4>
      <foo5>bar5</foo5>
    </foo4>
</foo1>

I have tried the xml.send method, but it converts the above nested hash to:

<foo1 foo3="bar3" foo4="foo5bar5" foo2="bar2"/>
<foo>bar</foo>

Answer 1

How about this?

class Hash
  def to_xml
    map do |k, v|
      text = Hash === v ? v.to_xml : v
      "<%s>%s</%s>" % [k, text, k]
    end.join
  end
end

h.to_xml
#=> "<foo>bar</foo><foo1><foo2>bar2</foo2><foo3>bar3</foo3><foo4><foo5>bar5</foo5></foo4></foo1>"

Answer 2

The accepted is a clean solution, but the below really does 'use' Nokogiri to construct XML from a Hash with special handling for attributes:

require 'nokogiri'

def generate_xml(data, parent = false, opt = {})
    return if data.to_s.empty?
    return unless data.is_a?(Hash)

    unless parent
        # assume that if the hash has a single key that it should be the root
        root, data = (data.length == 1) ? data.shift : ["root", data]
        builder = Nokogiri::XML::Builder.new(opt) do |xml|
            xml.send(root) {
                generate_xml(data, xml)
            }
        end

        return builder.to_xml
    end

    data.each { |label, value|
        if value.is_a?(Hash)
            attrs = value.fetch('@attributes', {})
            # also passing 'text' as a key makes nokogiri do the same thing
            text = value.fetch('@text', '') 
            parent.send(label, attrs, text) { 
                value.delete('@attributes')
                value.delete('@text')
                generate_xml(value, parent)
            }

        elsif value.is_a?(Array)
            value.each { |el|
                # lets trick the above into firing so we do not need to rewrite the checks
                el = {label => el}
                generate_xml(el, parent) 
            }

        else
            parent.send(label, value)
        end
    }
end

puts generate_xml(
    {'myroot' => 
        {
            'num' => 99, 
            'title' => 'something witty', 
            'nested' => { 'total' => [99, 98], '@attributes' => {'foo' => 'bar', 'hello' => 'world'}}, 
            'anothernest' => {
                '@attributes' => {'foo' => 'bar', 'hello' => 'world'}, 
                'date' => [
                    'today', 
                    {'day' => 23, 'month' => 'Dec', 'year' => {'y' => 1999, 'c' => 21}, '@attributes' => {'foo' => 'blhjkldsaf'}}
                ]
            }
    }})
puts puts
puts generate_xml({
            'num' => 99, 
            'title' => 'something witty', 
            'nested' => { 'total' => [99, 98], '@attributes' => {'foo' => 'bar', 'hello' => 'world'}}, 
            'anothernest' => {
                '@attributes' => {'foo' => 'bar', 'hello' => 'world'}, 
                'date' => [
                    'today', 
                    {'day' => [23,24], 'month' => 'Dec', 'year' => {'y' => 1999, 'c' => 21}, '@attributes' => {'foo' => 'blhjkldsaf'}}
                ]
            }
    })

And the resulting XML output:

<?xml version="1.0"?>
<myroot>
  <num>99</num>
  <title>something witty</title>
  <nested foo="bar" hello="world">
    <total>99</total>
    <total>98</total>
  </nested>
  <anothernest foo="bar" hello="world">
    <date>today</date>
    <date foo="blhjkldsaf">
      <day>23</day>
      <month>Dec</month>
      <year>
        <y>1999</y>
        <c>21</c>
      </year>
    </date>
  </anothernest>
</myroot>


<?xml version="1.0"?>
<root>
  <num>99</num>
  <title>something witty</title>
  <nested foo="bar" hello="world">
    <total>99</total>
    <total>98</total>
  </nested>
  <anothernest foo="bar" hello="world">
    <date>today</date>
    <date foo="blhjkldsaf">
      <day>23</day>
      <day>24</day>
      <month>Dec</month>
      <year>
        <y>1999</y>
        <c>21</c>
      </year>
    </date>
  </anothernest>
</root>

Answer 3

If you are using Rails you could use the built-in to_xml method.

c = { :foo => 'bar', :foo1 => { :foo2 => 'bar2', :foo3 => 'bar3', :foo4 => { :foo5 => 'bar5' }}}

xml = c.to_xml

=> "<?xml version=\"1.0\" encoding=\"UTF-8\"?>\n<hash>\n  <foo>bar</foo>\n  <foo1>\n    <foo2>bar2</foo2>\n    <foo3>bar3</foo3>\n    <foo4>\n      <foo5>bar5</foo5>\n    </foo4>\n  </foo1>\n</hash>\n"