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From: "Kyle X." <haebooty@yahoo.com>
Newsgroups: comp.lang.ruby
Subject: Re: Can you search in REXML by attributes?
Date: Mon, 11 Apr 2011 13:57:42 -0500
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> This works for me:
>
> $ cat noko.rb && ruby -rubygems noko.rb
> require 'nokogiri'
>
> doc = Nokogiri::XML(File.read("one.xml"))
> reference = doc.css("IfcCartesianPoint Coordinates
> IfcLengthMeasure").first
> puts reference.text
>
> 117.4
>
> But if I leave a space before IfcCartesianPoint in the call to the css
> method I get a parser error  (`on_error': unexpected ' ' after ''
> (Nokogiri::CSS::SyntaxError)). This is my file one.xml:
>
> <root xmlns:exp="http://foo" xmlns:xsi="http://bar">
>   <IfcWallStandardCase id="i1677">
>        <ObjectPlacement>
>          <IfcLocalPlacement xsi:nil="true" ref="i1671"/>
>       </ObjectPlacement>
>   </IfcWallStandardCase>
>
>   <IfcAxis2Placement3D id="i1671">
>      <Location>
>        <IfcCartesianPoint xsi:nil="true" ref="i1667"/>
>     </Location>
>   </IfcAxis2Placement3D>
>
>   <IfcCartesianPoint id="i1667">
>      <Coordinates id="i1670" exp:cType="list">
>          <IfcLengthMeasure exp:pos="0">117.4</IfcLengthMeasure>
>          <IfcLengthMeasure exp:pos="1">119.7</IfcLengthMeasure>
>          <IfcLengthMeasure exp:pos="2">0.</IfcLengthMeasure>
>       </Coordinates>
>   </IfcCartesianPoint>
> </root>
>
> This works too:
>
> doc.css("IfcCartesianPoint Coordinates IfcLengthMeasure").each {|el|
> puts el.text}
>
> Produces:
>
> 117.4
> 119.7
> 0.

Thank you for your reply.  When I continue to try and read the file I
have it keeps returning nil values and thus doesn't work.  But when I
copy and paste the xml you have written over the file I am trying to
read then it does work.  I understand that the path is slightly
different but using the xpath command-

doc.xpath("//IfcCartesianPoint/Coordinates/IfcLengthMeasure").each {|el|
puts el.text}

It should skip ahead to the first appearance of IfcCartesianPoint, much
the same as it works for using REXML xpath, no?  As this same sting of
IfcCartesianPoint/Coordinates/IfcLengthMeasure appears in this file.
Based on the documentation here -

(http://nokogiri.org/tutorials/searching_a_xml_html_document.html)

I think it should be working but it always returns nil.

I have attached the xml file I am trying to read and was wondering if
you could see where my error is occurring.  The first instance of
IfcCartesianPoint/Coordinates/IfcLengthMeasure appears on line 225.
>
> Maybe it's the way you are passing the file to Nokogiri::XML? By the
> way, in your way you are not closing the file handler. If you want to
> pass Nokogiri the file instead of reading it yourself you can do:
>
> doc = nil
> File.open("one.xml") {|f| doc = Nokogiri::XML(f)}
>
> or
>
> doc = File.open("one.xml") {|f| Nokogiri::XML(f)}
>
> This way, the file is properly closed.
>
> Jesus.

Is there an advantage to using .open vs .read?  The program I am writing
has to grab lots of information from the xml, maybe 300 items, would it
make a difference in speed to use one vs the other?  Also for me to read
a file at say c:\one.xml for it to read I have to write -
doc = File.open("/one.xml") {|f| Nokogiri::XML(f)}
Another form will not read including "\one.xml"

Thank you again for your time, you have been most helpful and it is
greatly appreciated.

Attachments:
http://www.ruby-forum.com/attachment/6114/one.xml


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