Re: XMLProcessing : testing optional value in a NodeModel

Hi,
The explanation is clear and rational, but given that there cannot be 
two attributes in one node with the same name, it feels 
counter-intuitive to think in terms of "a sequence" when dealing with 
node attributes, which probably explains why this sintax issues bites 
people regularly.

Coming from a XML/XSLT/Xpath background, I'm afraid FreeMarker's syntax 
to deal with XML does not feel intuitive. Using this case as an example, 
why would one want to check if the "sequence of attributes exist" 
(connection.@saveDir??) if the only way it can exist is if there is one, 
so I will always have to use (connection.@saveDir[0]??). The same thing 
happens in many cases with nodes, as checking if "it exists" is often 
useless as one has to check if the size of the sequence is greater than 
zero.

However, don't take that as a complain against FreeMarker. It's just 
that the syntax is "close" to XPath but "not that close" and that causes 
confusion to people with experience with XPath. And the "conditional 
handling code" is usually more verbose in FreeMarker.

Again, not a complain but an explanation why I think people have 
problems with this area. I'm very happy FM is even able to handle XML 
and I do appreciate it :).

S!
D.

Daniel Dekany escribió:
> Tuesday, February 5, 2008, 5:49:14 PM, thierry.henrio wrote:
> 
>> Hi all,
>>
>> I would like to conditionaly provide xml section if some attributes exists
>> in model
>>
>> here is my model
>> <?xml version="1.0" encoding="UTF-8"?>
>> <connection name="sle-001" template="sle-optional.ftl" saveDir="save">
>> </connection>
>>
>> model is parsed using dom api and a NodeModel is made out of it
>>
>> here is my template
>> <connections>
>>         <connection name="${connection.@name}" url="imc:gl:slev42">
>> <#if (connection.@saveDir)??>
> [snip]
> 
> The result of an expression like that is a node-set, as it can be not
> only a single node but multiple nodes as well, or 0 nodes. It's just
> like in XPath. Actually it's XPath syntactically ("@attName"). In the
> case of FreeMarker (with this ObjectWrapper anyway), the node-set is
> presented as a sequence of nodes. Thus the result itself is never
> "missing", it's just possibly an empty sequence. So, you had to write
> connection.@saveDir[0]??.


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