From: David Mitchell <david.mitchell@...>
Date: 2005-07-08T09:45:04+09:00
Subject: Re: Ruby in XML.

How does this work for loops? For example this won't work:

     <!-- for @i in 0...5 -->
       <img src="#{@i}.jpg"/>
     <!-- end -->

How would you suggest I achieve this? Perhaps:

     <!-- for @i in 0...5
            print "<img src='#{@i}.jpg'/>"
          end -->

I can quickly see that becoming an escaping nightmare.

I really like the idea but I would want it to be this flexible.

David

John Carter wrote:
> I have just stuck this on..
>   http://www.rubygarden.org/ruby?RubyInXML
> 
> I like XML.
> 
> There is a firm standard, there is a rich toolset to work on it.
> 
> I like HTML. It is simply the fastest way to deliver good looking 
> documents to the widest audience.
> 
> No surprise. I like XHTML it _is_ HTML in XML. I can validate my XHTML 
> documents and know that they conform exactly to the standard, and hence 
> will render properly on a wide set of browsers.
> 
> I love ruby. It is quite the easiest way to program. It has a lovely XML 
> API called REXML.
> 
> I sometimes need to do spreadsheet sort of things. Basically a document 
> that describes my reasoning and findings, supported by numbers.
> 
> Long time ago, when I still did Perl, I found by actual trials that I 
> was about as fast in Perl as the average guy is using a Spreadsheet. 
> Sometimes faster, sometimes slower. But for the next hundred data sets, 
> my perl scripts where a thousand times faster.
> 
> So I don't do spreadsheets these days, I write ruby scripts.
> 
> So I have taken to combining Ruby & HTML. Sometimes via cgi. It works 
> for me.
> 
> But sometimes I have documents that are more HTML than ruby. So it makes 
> sense to write them in HTML, with a bit of Ruby embedded. That's where 
> erb and eruby live.
> 
> But I don't like erb and eruby's tags. I can't validate my XHTML.
> 
> So add REXML and I present a very small script I call rubyexml. Ruby 
> Embedded in XML.
> 
> #!/usr/bin/ruby -w
> 
> require 'rexml/document'
> require 'rexml/streamlistener'
> require 'pp'
> 
> # All eval's are evaluated in the context of an instance of this class.
> # Extend this, or add this method to a class of your own.
> class Context
> 
>   def eval_value( value)
>     value.gsub( %r{ \#\{ ( [^\}]+ ) \} }x) do | match|
>       instance_eval( $1).to_s
>     end
>   end
> end
> 
> 
> # This does the work.
> class Listener
>   include REXML::StreamListener
> 
>   def initialize( context)
>     @context = context
>   end
> 
>   def comment( text)
>     print @context.instance_eval( text)
>   rescue SyntaxError => details
>     pp @context
>     pp text
>     raise "Failed to compile '#{text}' in context : #{details}"
>   end
> 
>   def tag_start(name,attrs)
>     print "<",name
>     attrs.each_pair do |key, value|
>       print " #{key}=\"#{@context.eval_value( value)}\""
>     end
>     print ">"
>   end
> 
>   def tag_end( name)
>     print "</", name, ">"
>   end
> 
>   def text( text)
>     print @context.eval_value(text)
>   end
> 
>   def cdata( ctext)
>     text( ctext)
>   end
> end
> 
> # This comes for free from REXML. Stream parse an XML document.
> REXML::Document::parse_stream( REXML::SourceFactory::create_from( 
> STDIN), Listener::new( Context.new))
> 
> 
> So take a chunk of XHTML...
> 
> <?xml version="1.0"?>
> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN"
> "xhtml11.dtd" >
> <html xmlns="HTTP://www.w3.org/TR/xhtml"
>    xmlns:xlink="HTTP://www.w3.org/XML/XLink/0.9"
>    xml:lang="en" >
>    <head>
>       <title>
> 
>     </title>
>    </head>
> 
>    <body>
>       <h1>
>          The answer to life, the universe and everything is <!-- 44 - 2 -->
>       </h1>
> 
>       <p>
>          The following image is   <!--  @file_name = 
> "pretty_picture.jpg" -->
> 
>          <img src="#{@file_name}" alt = "#{@file_name.sub(/\.jpg/,'')}"/>
>       </p>
>    </body>
> </html>
> 
> It validates as correct xml against the XHTML DTD.
> 
> Feed it through rubyexml and get...
> 
> <html xmlns:xlink="HTTP://www.w3.org/XML/XLink/0.9" xml:lang="en" 
> xmlns="HTTP://www.w3.org/TR/xhtml">
>    <head>
>       <title>
> 
>     </title>
>    </head>
> 
>    <body>
>       <h1>
>          The answer to life, the universe and everything is 42
>       </h1>
> 
>       <p>
>          The following image is   pretty_picture.jpg
> 
>          <img src="pretty_picture.jpg" alt="pretty_picture"></img>
>       </p>
>    </body>
> </html>
> 
> Just so blooming simple.
> 
> And if you have a big hairy object that knows all the deeper secrets of 
> life, just change rubyexml to...
> 
> REXML::Document::parse_stream( REXML::SourceFactory::create_from( 
> STDIN), Listener::new( BigHairyObjectThatKnowsTheDeeperSecretsOfLife.new))
> 
> And you can refer to all it's instance variables and methods.
> 
> It all so blooming simple!
> 
> 
> 
> John Carter                             Phone : (64)(3) 358 6639
> Tait Electronics                        Fax   : (64)(3) 359 4632
> PO Box 1645 Christchurch                Email : john.carter@tait.co.nz
> New Zealand
> 
> "At first I hoped that such a technically unsound project would
>  collapse but I soon realized it was doomed to success. Almost
>  anything in software can be implemented, sold, and even used given
>  enough determination. There is nothing a mere scientist can say that
>  will stand against the flood of a hundred million dollars. But there
>  is one quality that cannot be purchased in this way---and that is
>  reliability. The price of reliability is the pursuit of the utmost
>  simplicity. It is a price which the very rich find most hard to
>  pay." -- C.A.R. Hoare in The Emperor's Old Clothes,
>           Turing Award Lecture (27 October 1980)
> 
> 
> 
> 


-- 
David Mitchell
Software Engineer
Telogis