Ruby XPath 查找属性 [英] Ruby XPath to find Attribute

问题描述

哪些 Ruby 库可用于使用 XPath 选择属性，并将其用作其他 XPath 查询的起点.

What Ruby library can be used to select attribute using XPath, and to use it as the starting point for other XPath queries.

示例:

<root>
  <add key="A" value="B" />
  <add key="C" value="D" />
  <add foo="E" bar="F" />
</root>

所需代码:

get_pair "//*/@key", "../@value"
get_pair "//*/@foo", "../@bar"

预期输出:

"A" "B"
"C" "D"
"E" "F"

伪实现:

def get_pair(key, value)
  xml_doc.select[key].each do |a|
    puts [a, a.select[value]]
  end
end

推荐答案

你的出发点是 REXML

这里的挑战"是如何将属性节点视为子节点，这可以通过使用 单例方法，然后其他一切顺其自然:

The "challenge" here is how to treat an attribute node as a child node, and this can be done by using singleton methods, then everything else follows naturally:

require "rexml/document"
include REXML  # so that we don't have to prefix everything with REXML::...

def get_pair(xml_doc, key, value)
  XPath.each(xml_doc, key) do |node| 
    if node.is_a?(Attribute)
      def node.parent
        self.element
      end
    end
    puts "\"#{node}\" \"#{XPath.first(node, value)}\""
  end
end

xml_doc = Document.new <<EOF
  <root>
    <add key="A" value="B" />
    <add key="C" value="D" />
    <add foo="E" bar="F" />
  </root>
EOF

get_pair xml_doc, "//*/@key", "../@value"
get_pair xml_doc, "//*/@foo", "../@bar"

产生:

"A" "B"
"C" "D"
"E" "F"

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