XML Data Binding for Ruby?

ruby-talk
1

hello

I am currently preparing an article about Ruby and XML where I will
show some XML modules for ruby. only a short example to show
people what’s possible and that Ruby is a great alternative to Java/C#
when processing XML.

I am searching for a module where I can construct a Ruby Class from
an arbitrary XML document, similar to Python’s anobind

with this I can take an XML document like this

<?xml version="1.0"?> White-tailed Eagle Seeadler Kestrel Turmfalke

and this python code

···

=============
#!/usr/bin/env python

import anobind
from Ft.Xml import InputSource
from Ft.Lib import Uri

file_uri = Uri.OsPathToUri(‘raptors.xml’, attemptAbsolute=1)
input_source = InputSource.DefaultFactory.fromUri(file_uri)

binding = anobind.binder().read_xml(input_source)

print binding.birds.raptor[0].german_name.text_content()
print

for raptor in binding.birds.raptor:
print raptor.wingspan
print raptor.german_name.text_content()
print raptor.english_name.text_content()
print

is there something similar for ruby ?

thanks in advance

regards

Markus

2

Markus Jais markusjais@yahoo.de wrote in message news:c78pel$11lbg$1@ID-75083.news.uni-berlin.de…

with this I can take an XML document like this
…
and this python code

#!/usr/bin/env python

import anobind

Here’s something that’ll do the job. I just threw this together, so
it is probably fragile, and it is one-way – it only converts XML to
Ruby objects. But it implements the functionality that you described
in the example you gave – it does so in 25 lines of code, and took
about as many minutes to write and test. :slight_smile: I’m sure it could be
compressed and/or optimized; there were a number of solutions to
choose from.

By the way, I personally believe that this class of XML-to-Objects
mechanism has extremely limited use. If you use real XML objects and
XPath, you have access to a much broader set of XML documents, and it
is often easier to work with – especially with deeply nested XML.
And if all you’re looking for is serialization, there are a number of
projects available; some, even, that generate XML – albeit, not as
clear of a 1-to-1 mapping as here.

For an example of where I expect the Python code to fail (and I know
the Ruby code I’ve supplied will fail), given:

B2 TAG1 TAG2 <:tag>TAG3

How do you differentiate between @b and b? Can you get any of the TAG
text values?

Anyway, here’s the Ruby version of the Python module.

############## START CODE

A quasi-serialization class. Accepts a limited subset of XML and

turns it

into Ruby objects.

require “rexml/document”

class XMLObject
def initialize element
@element = element
@methods = {}
end
def method_missing method
m_name = method.to_s
return @methods[m_name] if @methods[m_name]
el = REXML::XPath.match( @element, m_name )
case el.size
when 0
return @element.attributes[ m_name ]
when 1
@methods[ m_name ] = XMLObject.new( el[0] )
else
el.collect!{ |e| XMLObject.new( e ) }
@methods[ m_name ] = el
end
return @methods[m_name]
end
def to_s
return REXML::XPath.match( @element, “text()” ).join.squeeze("
\n\t").strip
end
end

Cut here if you want to reuse this code. Everything that follows is

just an example of how it works.

d = REXML::Document.new( DATA.read )
a = XMLObject.new( d.root )
puts “a.b.x = #{a.b.x}”
puts “a.b.to_s = #{a.b.to_s}”
puts “a.b.c[0].y = #{a.b.c[0].y}”
puts “a.b.c[1].to_s = #{a.b.c[1].to_s}”

END


C1
C2
Text

— SER

3

thanks a lot.

markus

Sean Russell wrote:

···

Markus Jais markusjais@yahoo.de wrote in message
news:c78pel$11lbg$1@ID-75083.news.uni-berlin.de…

with this I can take an XML document like this
…
and this python code

#!/usr/bin/env python

import anobind

Here’s something that’ll do the job. I just threw this together, so
it is probably fragile, and it is one-way – it only converts XML to
Ruby objects. But it implements the functionality that you described
in the example you gave – it does so in 25 lines of code, and took
about as many minutes to write and test. :slight_smile: I’m sure it could be
compressed and/or optimized; there were a number of solutions to
choose from.

By the way, I personally believe that this class of XML-to-Objects
mechanism has extremely limited use. If you use real XML objects and
XPath, you have access to a much broader set of XML documents, and it
is often easier to work with – especially with deeply nested XML.
And if all you’re looking for is serialization, there are a number of
projects available; some, even, that generate XML – albeit, not as
clear of a 1-to-1 mapping as here.

For an example of where I expect the Python code to fail (and I know
the Ruby code I’ve supplied will fail), given:

B2 TAG1 TAG2 <:tag>TAG3

How do you differentiate between @b and b? Can you get any of the TAG
text values?

Anyway, here’s the Ruby version of the Python module.

############## START CODE

A quasi-serialization class. Accepts a limited subset of XML and

turns it

into Ruby objects.

require “rexml/document”

class XMLObject
def initialize element
@element = element
@methods = {}
end
def method_missing method
m_name = method.to_s
return @methods[m_name] if @methods[m_name]
el = REXML::XPath.match( @element, m_name )
case el.size
when 0
return @element.attributes[ m_name ]
when 1
@methods[ m_name ] = XMLObject.new( el[0] )
else