Re: Dynamic list

Wednesday, February 25, 2009, 4:48:56 PM, Kirill wrote:
> Hi Daniel,
>
> Here is the scenario. Let's say I have this XML as an input (data- 
> model):
> <root>
>         <parent1>
>                 <child1>text</child1>
>                 <child1>text</child1>
>         </parent1>
>         <parent2>text</parent2>
>         <parent2>text</parent2>
>         <parent2>text</parent2>
> </root>
>
> Based on the template I use and more specifically, this part  
> (simplified):
>
> <#macro @element>
>     <#-- this emits an opening tag -->
>     <${.node?node_name} <#if!.node?children?has_content>/</#if>>
>
>     <#-- this emits variable name, with proper formatting -->
>     <#if .node?children?size = 1>
>         ${r"${"}${.node?node_name}${r"}"}
>     </#if>
>
>     <#if .node?children?size &gt; 0>
>         <#recurse>
>     </#if>
>
>     <#-- this emits closing tag -->
>     <#if .node?children?has_content>
>     </${.node?node_name}>
>     </#if>
> </#macro>
>
>
> The output will be this:
>
> <root>
>         <parent1>
>                 <child1>${child1}</child1>
>                 <child1>${child1}</child1>
>         </parent1>
>         <parent2>${child2}</parent2>
>         <parent2>${child2}</parent2>
>         <parent2>${child2}</parent2>
> </root>
>                 
> What I'd like to achieve is this:
>
> <root>
>         <parent1>
>                 <#list child1 as childItem1>
>                         <child1>${childItem1}</child1>
>                 </#list>
>         </parent1>
>         <#list parent2 as parentItem2>
>                 <parent2>${parentItem2}
>         </#list>
> </root>
>
> So, basically, instead of outputting tags with the same name, create a
> list of such items.
>
> In this particular case, Freemarker has to detect if there is more  
> than one element with a same name,
> and if there is - create a list of those elements.
>
> I've managed to find a workaround, with a simple test variable, and by
> appending [0], [1], etc to variable names.
> But <#list> should look a lot better though, and easier to understand
> for template users.

Ugh... not exactly an MVC application of the template language. I
prefer pushing much more "cooked" data-models to templates, otherwise
they cease to be templates (template: a program that looks similarly
to its own output). Anyway, if you want to do everything in the
template, I think that to do this with #list, you had to know the list
of all element *names* that will occur as a child. I mean, regardless
of how many times a certain kind of child occurs, that list would
contain its name only once. Let's say you write a function for this,
"allChildNames". Then you could do something like this:

<#list allChildNames(.node) as childName>
  <#list .node[childName] as child>
     ${child}
  </#list>
</#list>

The allChildNames can be easily implemented even in pure FTL, using
the trick:

  <#if names?contains(newName)>
    <#assign names = names + [newName]>
  </#if>

but for bigger XML-s that will *quickly* become slow, so then you
better implement it in Java (see
freemarker.template.TemplateMethodModelEx), using a HashSet or
something.


> Thanks again for your input.
>
> Cheers,
> Kirill

-- 
Best regards,
 Daniel Dekany


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