From: Robert Klemme <shortcutter@...>
Date: 2011-04-20T16:46:44+09:00
Subject: Re: Nokogiri parsing question

On Wed, Apr 20, 2011 at 9:27 AM, Kyle X. <haebooty@yahoo.com> wrote:
> Hello, I have beenhaving trouble trying to transform some REXML to
> Nokogiri, and from my reading online I cannot find the proper way to
> write it using Nokogiri.  Here are the two examples I am having trouble
> with:
>
> Case 1)
> <IfcWallStandardCase id="i17855">
>  <Representation>
>    <IfcProductDefinitionShape id="i17925">
>      <Representations id="i17928" exp:cType="list">
>        <IfcShapeRepresentation exp:pos="0" xsi:nil="true"
> ref="i17886"/>
>        <IfcShapeRepresentation exp:pos="1" xsi:nil="true"
> ref="i17919"/>
>      </Representations>
>    </IfcProductDefinitionShape>
>  </Representation>
> </IfcWallStandardCase>
>
> I am trying to get the reference for exp:pos="1", and I had this working
> with using REXML with the following -
>
> XPath.match( $doc, "//IfcWallStandardCase//*[@pos='1']" )
>
> With nokogiri I can get it to read both pos 0 and 1, using .css and
> .xpath-
>
> $doc_noko.css("uosNS|IfcWallStandardCase uosNS|IfcShapeRepresentation",
> {"uosNS" => $http})
> and
> $doc_noko.xpath("//uosNS:IfcWallStandardCase//uosNS:IfcShapeRepresentation",
> {"uosNS" => $http})
>
> But cannot figure out how to get it to read only pos=1 using either
> method and continuously get error or nil.

The XPath seems to work in Nokogiri as well:

irb(main):017:0> puts(doc.xpath "//IfcWallStandardCase//*[@pos='1']")
<IfcShapeRepresentation pos="1" nil="true" ref="i17919"/>
=> nil

> Case 2)
> <IfcDirection id="i1574">
>  <DirectionRatios id="i1577" exp:cType="list">
>    <exp:double-wrapper pos="0">1.</exp:double-wrapper>
>    <exp:double-wrapper pos="1">0.</exp:double-wrapper>
>    <exp:double-wrapper pos="2">0.</exp:double-wrapper>
>  </DirectionRatios>
> </IfcDirection>
>
> The issue I am having here is that I am reading this with Nokogiri using
> .xpath and the colon in exp:double is giving me trouble since the xpath
> is written -
>
> ref = "i1574"
> $doc_noko.xpath("//uosNS:*[@id='#{ref}']//uosNS:exp:double-wrapper",
> {"uosNS" => $http}).map {|element| element.text}
>
> I am guessing that it would be easier to use .css here rather than
> .xpath.  So I have tried using it but cannot seem to get it correct.
> Trying -
>
> ref = "i1574"
> $doc_noko.css("uosNS|#{ref} uosNS|exp:double-wrapper", {"uosNS" =>
> $http}).map {|element| element.text}
>
> I read in a previous post that you call the ref using #{} for css,
> but this returns nil for me.

When I define a namespace mapping and remove the namespace prefix from
the wildcard it works as expected:

irb(main):042:0> doc=Nokogiri.XML(<<XML)
irb(main):043:1" <IfcDirection xmlns:exp="foo" id="i1574">
irb(main):044:1"  <DirectionRatios id="i1577" exp:cType="list">
irb(main):045:1"    <exp:double-wrapper pos="0">1.</exp:double-wrapper>
irb(main):046:1"    <exp:double-wrapper pos="1">0.</exp:double-wrapper>
irb(main):047:1"    <exp:double-wrapper pos="2">0.</exp:double-wrapper>
irb(main):048:1"  </DirectionRatios>
irb(main):049:1" </IfcDirection>
irb(main):050:1" XML

Note: "exp" is mapped to "foo".

irb(main):052:0> ref
=> "i1574"

irb(main):054:0> puts
doc.xpath("//*[@id='#{ref}']//ns1:double-wrapper", {"ns1" => "foo"})
<exp:double-wrapper pos="0">1.</exp:double-wrapper>
<exp:double-wrapper pos="1">0.</exp:double-wrapper>
<exp:double-wrapper pos="2">0.</exp:double-wrapper>
=> nil

With ns prefix:

irb(main):055:0> puts
doc.xpath("//ns1:*[@id='#{ref}']//ns1:double-wrapper", {"ns1" =>
"foo"})
=> nil

Kind regards

robert

-- 
remember.guy do |as, often| as.you_can - without end
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