Monday, October 19, 2009, 11:03:20 AM, Chris Lu wrote:
> How to programatically find out what variables a template needs?
>
> Let's say I have a template, and I want to get a list of variables the
> template uses, and then prompt the user for the missing variables.
>
> Is it possible?
In short, no.
In detail, there are two problems here:
- The inherent problem: The language is too dynamic for that. You
don't know what data-model variables will be get with
.data[dynamicName], you don't know if which conditional parts will
be executed, and, let's not forget, since data-model variables can
be hidden (#assign, #global, #local...), it's at best difficult to
tell if ${foo} refers to a data-model variable or not. And, of
course, if call macros, those may refer to data-model variables
internally too...
- Problems with the current API: For very trivial templates, you may
try to make a good guess by traversing the template starting out
with template.getRootTreeNode(), however, most node classes are not
public, and I'm not sure how much can you reliably extract from the
results of the common freemarker.core.TemplateElement methods.
Anyway, this part of the API will be totally revisited in 2.4,
exactly because it's lame in 2.3.x (but who knows when 2.4 will be
released...). Plus, due to issues with Google App Engine we may will
have to substitute the Swing API-s used by the mentioned 2.3 tree
traversal API-s with our owns, which is then not backward-compatible
(but otherwise easy to adapt to).
> Chris
--
Best regards,
Daniel Dekany
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