Rails nokogiri parse XML file - ruby-on-rails

Question

I'm a little bit confused: could not find in web good examples of parsing xml with nokogiri...
example of my data:
<?xml version="1.0" encoding="UTF-8"?>
<root>
<rows SessionGUID="6448680D1">
<row>
<AnalogueCode>0451103079</AnalogueCode>
<AnalogueCodeAsIs>0451103079</AnalogueCodeAsIs>
<AnalogueManufacturerName>BOSCH</AnalogueManufacturerName>
<AnalogueWeight>0.000</AnalogueWeight>
<CodeAsIs>OC90</CodeAsIs>
<DeliveryVariantPriceAKiloForClientDescription />
<DeliveryVariantPriceAKiloForClientPrice>0.00</DeliveryVariantPriceAKiloForClientPrice>
<DeliveryVariantPriceNote />
<PriceListItemDescription />
<PriceListItemNote />
<IsAvailability>1</IsAvailability>
<IsCross>1</IsCross>
<LotBase>1</LotBase>
<LotType>1</LotType>
<ManufacturerName>KNECHT/MAHLE</ManufacturerName>
<OfferName>MSC-STC-58</OfferName>
<PeriodMin>2</PeriodMin>
<PeriodMax>4</PeriodMax>
<PriceListDiscountCode>31087</PriceListDiscountCode>
<ProductName>Фильтр масляный</ProductName>
<Quantity>41</Quantity>
<SupplierID>30</SupplierID>
<GroupTitle>Замена</GroupTitle>
<Price>203.35</Price>
</row>
<row>
<AnalogueCode>0451103079</AnalogueCode>
<AnalogueCodeAsIs>0451103079</AnalogueCodeAsIs>
<AnalogueManufacturerName>BOSCH</AnalogueManufacturerName>
<AnalogueWeight>0.000</AnalogueWeight>
<CodeAsIs>OC90</CodeAsIs>
<DeliveryVariantPriceAKiloForClientDescription />
<DeliveryVariantPriceAKiloForClientPrice>0.00</DeliveryVariantPriceAKiloForClientPrice>
<DeliveryVariantPriceNote />
<PriceListItemDescription />
<PriceListItemNote>[0451103079] Bosch,MTGC#0451103079</PriceListItemNote>
<IsAvailability>1</IsAvailability>
<IsCross>1</IsCross>
<LotBase>1</LotBase>
<LotType>0</LotType>
<ManufacturerName>KNECHT/MAHLE</ManufacturerName>
<OfferName>MSC-STC-1303</OfferName>
<PeriodMin>3</PeriodMin>
<PeriodMax>5</PeriodMax>
<PriceListDiscountCode>102134</PriceListDiscountCode>
<ProductName>Фильтр масляный</ProductName>
<Quantity>5</Quantity>
<SupplierID>666</SupplierID>
<GroupTitle>Замена</GroupTitle>
<Price>172.99</Price>
</row>
</rows>
</root>
and ruby code:
...
xml_doc = Nokogiri::XML(response.body)
parts = xml_doc.xpath('/root/rows/row')
with the help of xpath i could do this? also how to get this parts object (row)?

Answer 1

You're on the right track. parts = xml_doc.xpath('/root/rows/row') gives you back a NodeSet i.e. a list of the <row> elements.
You can loop through these using each or use row indexes like parts[0], parts[1] to access specific rows. You can then get the values of child nodes using xpath on the individual rows.
e.g. you could build a list of the AnalogueCode for each part with:
codes = []
parts.each do |row|
codes << row.xpath('AnalogueCode').text
end
Looking at the full example of the XML you're processing there are 2 issues preventing your XPath from matching:
the <root> tag isn't actually the root element of the XML so /root/.. doesn't match
The XML is using namespaces so you need to include these in your XPaths
so there are a couple of possible solutions:
use CSS selectors rather than XPaths (i.e. use search) as suggested by the Tin Man
after xml_doc = Nokogiri::XML(response.body) do xml_doc.remove_namespaces! and then use parts = xml_doc.xpath('//root/rows/row') where the double slash is XPath syntax to locate the root node anywhere in the document
specify the namespaces:
e.g.
xml_doc = Nokogiri::XML(response.body)
ns = xml_doc.collect_namespaces
parts = xml_doc.xpath('//xmlns:rows/xmlns:row', ns)
codes = []
parts.each do |row|
codes << xpath('xmlns:AnalogueCode', ns).text
end
I would go with 1. or 2. :-)

Answer 2

First, Nokogiri supports XPath AND CSS. I recommend using CSS because it's more easily read:
doc.search('row')
will return a NodeSet of every <row> in the document.
The equivalent XPath is:
doc.search('//row')
...how to get this parts object (row)?
I'm not sure what that means, but if you want to access individual elements inside a <row>, it's easily done several ways.
If you only want one node inside each of the row nodes:
doc.search('row Price').map(&:to_xml)
# => ["<Price>203.35</Price>", "<Price>172.99</Price>"]
doc.search('//row/Price').map(&:to_xml)
# => ["<Price>203.35</Price>", "<Price>172.99</Price>"]
If you only want the first such occurrence, use at, which is the equivalent of search(...).first:
doc.at('row Price').to_xml
# => "<Price>203.35</Price>"
Typically we want to iterate over a number of blocks and return an array of hashes of the data found:
row_hash = doc.search('row').map{ |row|
{
AnalogueCode: row.at('AnalogueCode').text,
Price: row.at('Price').text,
}
}
row_hash
# => [{:AnalogueCode=>"0451103079", :Price=>"203.35"},
# {:AnalogueCode=>"0451103079", :Price=>"172.99"}]
These are ALL covered in Nokogiri's tutorials and are answered many times here on Stack Overflow, so take the time to read and search.