How do I use Nokogiri to parse an XML file?

ruby xml parsing nokogiri
camdixon picture camdixon · Jul 11, 2013 · Viewed 28.6k times · Source

I'm having some issues with Nokogiri.

I am trying to parse this XML file:

<Collection version="2.0" id="74j5hc4je3b9">
  <Name>A Funfair in Bangkok</Name>
  <PermaLink>Funfair in Bangkok</PermaLink>
  <PermaLinkIsName>True</PermaLinkIsName>
  <Description>A small funfair near On Nut in Bangkok.</Description>
  <Date>2009-08-03T00:00:00</Date>
  <IsHidden>False</IsHidden>
  <Items>
    <Item filename="AGC_1998.jpg">
      <Title>Funfair in Bangkok</Title>
      <Caption>A small funfair near On Nut in Bangkok.</Caption>
      <Authors>Anthony Bouch</Authors>
      <Copyright>Copyright © Anthony Bouch</Copyright>
      <CreatedDate>2009-08-07T19:22:08</CreatedDate>
      <Keywords>
        <Keyword>Funfair</Keyword>
        <Keyword>Bangkok</Keyword>
        <Keyword>Thailand</Keyword>
      </Keywords>
      <ThumbnailSize width="133" height="200" />
      <PreviewSize width="532" height="800" />
      <OriginalSize width="2279" height="3425" />
    </Item>
    <Item filename="AGC_1164.jpg" iscover="True">
      <Title>Bumper Cars at a Funfair in Bangkok</Title>
      <Caption>Bumper cars at a small funfair near On Nut in Bangkok.</Caption>
      <Authors>Anthony Bouch</Authors>
      <Copyright>Copyright © Anthony Bouch</Copyright>
      <CreatedDate>2009-08-03T22:08:24</CreatedDate>
      <Keywords>
        <Keyword>Bumper Cars</Keyword>
        <Keyword>Funfair</Keyword>
        <Keyword>Bangkok</Keyword>
        <Keyword>Thailand</Keyword>
      </Keywords>
      <ThumbnailSize width="200" height="133" />
      <PreviewSize width="800" height="532" />
      <OriginalSize width="3725" height="2479" />
    </Item>
  </Items>
</Collection>

I want all of that information displayed to the screen, that's it. Should be simple right? I am doing this:

require 'nokogiri'

doc = Nokogiri::XML(File.open("sample.xml"))
@block = doc.css("items item").map {|node| node.children.text}
puts @block

Each Items is a node, and under that there are children nodes of Item?

I create a map of this, which returns a hash, and the code in {} goes through each node and places the children text into @block. Then I can display all of the child node's text to the screen.

I have no idea how far or close I am, because I've read so many articles, and am still a little confused on the basics especially since usually with a new language, I read from a file and output to the screen for a basic program.

Answer

Arup Rakshit picture Arup Rakshit · Jul 11, 2013

Here I will try to explain you all the questions/confusions you are having:

require 'nokogiri'

doc = Nokogiri::XML.parse <<-XML
<Collection version="2.0" id="74j5hc4je3b9">
  <Name>A Funfair in Bangkok</Name>
  <PermaLink>Funfair in Bangkok</PermaLink>
  <PermaLinkIsName>True</PermaLinkIsName>
  <Description>A small funfair near On Nut in Bangkok.</Description>
  <Date>2009-08-03T00:00:00</Date>
  <IsHidden>False</IsHidden>
  <Items>
    <Item filename="AGC_1998.jpg">
      <Title>Funfair in Bangkok</Title>
      <Caption>A small funfair near On Nut in Bangkok.</Caption>
      <Authors>Anthony Bouch</Authors>
      <Copyright>Copyright © Anthony Bouch</Copyright>
      <CreatedDate>2009-08-07T19:22:08</CreatedDate>
      <Keywords>
        <Keyword>Funfair</Keyword>
        <Keyword>Bangkok</Keyword>
        <Keyword>Thailand</Keyword>
      </Keywords>
      <ThumbnailSize width="133" height="200" />
      <PreviewSize width="532" height="800" />
      <OriginalSize width="2279" height="3425" />
    </Item>
    <Item filename="AGC_1164.jpg" iscover="True">
      <Title>Bumper Cars at a Funfair in Bangkok</Title>
      <Caption>Bumper cars at a small funfair near On Nut in Bangkok.</Caption>
      <Authors>Anthony Bouch</Authors>
      <Copyright>Copyright © Anthony Bouch</Copyright>
      <CreatedDate>2009-08-03T22:08:24</CreatedDate>
      <Keywords>
        <Keyword>Bumper Cars</Keyword>
        <Keyword>Funfair</Keyword>
        <Keyword>Bangkok</Keyword>
        <Keyword>Thailand</Keyword>
      </Keywords>
      <ThumbnailSize width="200" height="133" />
      <PreviewSize width="800" height="532" />
      <OriginalSize width="3725" height="2479" />
    </Item>
  </Items>
</Collection>
XML

So from my understanding of Nokogiri, each 'Items' is a node, and under that there are children nodes of 'Item'?

No, each Items are Nokogiri::XML::NodeSet. And under that there are 2 children nodes of Items,which are of Nokogiri::XML::Element class object. You can say them also Nokogiri::XML::Node

doc.class # => Nokogiri::XML::Document
@block = doc.xpath("//Items/Item")
@block.class # => Nokogiri::XML::NodeSet
@block.count # => 2
@block.map { |node| node.name }
# => ["Item", "Item"]
@block.map { |node| node.class }
# => [Nokogiri::XML::Element, Nokogiri::XML::Element]
@block.map { |node| node.children.count }
# => [19, 19]
@block.map { |node| node.class.superclass }
# => [Nokogiri::XML::Node, Nokogiri::XML::Node]

We create a map of this, which returns a hash I believe, and the code in {} goes through each node and places the children text into @block. Then I can display all of this child node's text to the screen.

I don't understand this. Although I tried to explain below to show what is Node,and what is Nodeset in Nokogiri. Remember Nodeset is a collection of Nodes.

@chld_class = @block.map do |node|
  node.children.class
end
@chld_class
# => [Nokogiri::XML::NodeSet, Nokogiri::XML::NodeSet]
@chld_name = @block.map do |node|
  node.children.map { |n| [n.name,n.class] }
end
@chld_name
# => [[["text", Nokogiri::XML::Text],
#      ["Title", Nokogiri::XML::Element],
#      ["text", Nokogiri::XML::Text],
#      ["Caption", Nokogiri::XML::Element],
#      ["text", Nokogiri::XML::Text],
#      ["Authors", Nokogiri::XML::Element],
#      ["text", Nokogiri::XML::Text],
#      ["Copyright", Nokogiri::XML::Element],
#      ["text", Nokogiri::XML::Text],
#      ["CreatedDate", Nokogiri::XML::Element],
#      ["text", Nokogiri::XML::Text],
#      ["Keywords", Nokogiri::XML::Element],
#      ["text", Nokogiri::XML::Text],
#      ["ThumbnailSize", Nokogiri::XML::Element],
#      ["text", Nokogiri::XML::Text],
#      ["PreviewSize", Nokogiri::XML::Element],
#      ["text", Nokogiri::XML::Text],
#      ["OriginalSize", Nokogiri::XML::Element],
#      ["text", Nokogiri::XML::Text]],
#     [["text", Nokogiri::XML::Text],
#      ["Title", Nokogiri::XML::Element],
#      ["text", Nokogiri::XML::Text],
#      ["Caption", Nokogiri::XML::Element],
#      ["text", Nokogiri::XML::Text],
#      ["Authors", Nokogiri::XML::Element],
#      ["text", Nokogiri::XML::Text],
#      ["Copyright", Nokogiri::XML::Element],
#      ["text", Nokogiri::XML::Text],
#      ["CreatedDate", Nokogiri::XML::Element],
#      ["text", Nokogiri::XML::Text],
#      ["Keywords", Nokogiri::XML::Element],
#      ["text", Nokogiri::XML::Text],
#      ["ThumbnailSize", Nokogiri::XML::Element],
#      ["text", Nokogiri::XML::Text],
#      ["PreviewSize", Nokogiri::XML::Element],
#      ["text", Nokogiri::XML::Text],
#      ["OriginalSize", Nokogiri::XML::Element],
#      ["text", Nokogiri::XML::Text]]]

@chld_name = @block.map do |node|
  node.children.map{|n| [n.name,n.text.strip] if n.elem? }.compact
end.compact
@chld_name
# => [[["Title", "Funfair in Bangkok"],
#      ["Caption", "A small funfair near On Nut in Bangkok."],
#      ["Authors", "Anthony Bouch"],
#      ["Copyright", "Copyright © Anthony Bouch"],
#      ["CreatedDate", "2009-08-07T19:22:08"],
#      ["Keywords", "Funfair\n        Bangkok\n        Thailand"],
#      ["ThumbnailSize", ""],
#      ["PreviewSize", ""],
#      ["OriginalSize", ""]],
#     [["Title", "Bumper Cars at a Funfair in Bangkok"],
#      ["Caption", "Bumper cars at a small funfair near On Nut in Bangkok."],
#      ["Authors", "Anthony Bouch"],
#      ["Copyright", "Copyright © Anthony Bouch"],
#      ["CreatedDate", "2009-08-03T22:08:24"],
#      ["Keywords",
#       "Bumper Cars\n        Funfair\n        Bangkok\n        Thailand"],
#      ["ThumbnailSize", ""],
#      ["PreviewSize", ""],
#      ["OriginalSize", ""]]]

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