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up vote 3 down vote favorite 
data =
[ { 'name' => 'category1',
    'subCategory' => [ {'name' => 'subCategory1',
                        'product' => [ {'name' => 'prodcutName1',
                                        'desc' => 'desc1'},
                                       {'name' => 'prodcutName2',
                                        'desc' => 'desc2'}]
                        } ]

  },
  { 
    #category2 ...and so on 
  }
]

Just recently finished a small project with Ruby. I used the above array of hashes to produce a XML.

I think my solution is quite messy nesting loops and builder tags. Can anyone help me out with a more elegant approach? 

builder = Nokogiri::XML::Builder.new { |xml|
data.each { |category| # go through every category in the data array
    xml.category {
        xml.name category['name']
        category['subCategory'].each { |subCategory| # go through each subCategory in the category
            xml.subCategory {
                xml.name subCategory['name']
                subCategory['product'].each { |product| # go though each products and print their data
                    xml.name product['name']
                    xml.desc product['desc']
                }
            }
        }
    }
}


puts builder.to_xml
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migrated from stackoverflow.com May 23 at 18:15

This question came from our site for professional and enthusiast programmers.
    
Are you able to change the source data hash to a different format? –  Phrogz May 16 at 4:34
    
@Phrogz No, the source needs to stay as it is. –  yummisashimi May 16 at 4:44

2 Answers 2

up vote 3 down vote accepted

Here's a nice recursive solution, that creates <key>value</key> from 'key'=>'value' entries in your hash. If the value is an array, it instead recurses, using the key name as a wrapper element.

require 'nokogiri'

def process_array(label,array,xml)
  array.each do |hash|
    xml.send(label) do                 # Create an element named for the label
      hash.each do |key,value|
        if value.is_a?(Array)
          process_array(key,value,xml) # Recurse
        else
          xml.send(key,value)          # Create <key>value</key> (using variables)
        end
      end
    end
  end
end

builder = Nokogiri::XML::Builder.new do |xml|
  xml.root do                           # Wrap everything in one element.
    process_array('category',data,xml)  # Start the recursion with a custom name.
  end
end

puts builder.to_xml

When used with this data…

data = [
  { 'name' => 'category1',
    'subCategory' => [
      { 'name' => 'subCategory1',
        'product' => [
          { 'name' => 'productName1',
            'desc' => 'desc1' },
          { 'name' => 'productName2',
            'desc' => 'desc2' } ]
      } ]
  },
  { 'name' => 'category2',
    'subCategory' => [
      { 'name' => 'subCategory2.1',
        'product' => [
          { 'name' => 'productName2.1.1',
            'desc' => 'desc1' },
          { 'name' => 'productName2.1.2',
            'desc' => 'desc2' } ]
      } ]
  },
]

…you get this result:

<?xml version="1.0"?>
<root>
  <category>
    <name>category1</name>
    <subCategory>
      <name>subCategory1</name>
      <product>
        <name>productName1</name>
        <desc>desc1</desc>
      </product>
      <product>
        <name>productName2</name>
        <desc>desc2</desc>
      </product>
    </subCategory>
  </category>
  <category>
    <name>category2</name>
    <subCategory>
      <name>subCategory2.1</name>
      <product>
        <name>productName2.1.1</name>
        <desc>desc1</desc>
      </product>
      <product>
        <name>productName2.1.2</name>
        <desc>desc2</desc>
      </product>
    </subCategory>
  </category>
</root>

However, if I had control over the XML schema, I'd do this instead:

require 'nokogiri'

def process_array(label,array,xml)
  array.each do |hash|
    kids,attrs = hash.partition{ |k,v| v.is_a?(Array) }
    xml.send(label,Hash[attrs]) do
      kids.each{ |k,v| process_array(k,v,xml) }
    end
  end
end

builder = Nokogiri::XML::Builder.new do |xml|
  xml.root{ process_array('category',data,xml) }
end

puts builder.to_xml


<?xml version="1.0"?>
<root>
  <category name="category1">
    <subCategory name="subCategory1">
      <product name="productName1" desc="desc1"/>
      <product name="productName2" desc="desc2"/>
    </subCategory>
  </category>
  <category name="category2">
    <subCategory name="subCategory2.1">
      <product name="productName2.1.1" desc="desc1"/>
      <product name="productName2.1.2" desc="desc2"/>
    </subCategory>
  </category>
</root>

…but perhaps you're dealing with some terrible XML schema like PList.

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up vote 0 down vote

A very clean approach is to use the xml-simple gem. Simply use xml_out with two options:

  • RootName to specify the XML root element
  • AnonymousTag to provide a tag name for your top-level hash

Other options are documented here.

Code:

require 'xmlsimple'
XmlSimple.xml_out(data, {"RootName" => "categories", "AnonymousTag => "category"})

Output:

<categories>
  <category name="category1">
    <subCategory name="subCategory1">
      <product name="prodcutName1" desc="desc1" />
      <product name="prodcutName2" desc="desc2" />
    </subCategory>
  </category>
  <category></category>
</categories>
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