Re: instanceOf and/or isAssignableFrom operator in freemarker

Thursday, April 23, 2009, 1:07:47 PM, Daniel Dekany wrote:
> Wednesday, April 22, 2009, 8:49:41 PM, dlevancho wrote:
>>
>> Hi,
>>
>> I am trying to find a way to test if a certain object implements certain
>> Interface, or at lease if it is instance eof certain class,but as I
>> understand freemarker does not support that operator?
>
> It doesn't. I mean, not out-of-the-box. The template language (FTL)
> doesn't even know the idea of classes, it only has numbers, string,
> boolean, hashes, sequences, and a few more such basic types. Actually,
> this issues is pretty clearly data-model related (certain entries in
> the data-model should be able to tell if they are a YouKnowWhat).
>
>> I would low to see a isAssignableFrom check or at least instanceOf
>> operator, but so far I have not seen a word mention about them in
>> freemarker manual . can anyone help me out with a workaround?
>
> For now, you can either write a TemplatMethodModel

Sorry, a TemplateMethodModelEx...

> for it, or extend
> the object wrapper (BeansWrapper). Or, maybe you can use duck-typing.
> I believe this is pretty clearly a data-model issue, and as such I
> would advise to solve it be customizing BeansWrapper (see also:
> Configuration.setObjectWrapper).
>
> Actually, Attila, can't BeansWrapper already do that? I don't know...
> I guess it should be able to, given it *is* for exposing Java object
> as-is (OK, with some security restrictions and like, but you get what
> I mean), and the class is a quite important information for Java
> classes,

For java objects, I meant...

> given that in the Java world duck-typing and like is at best rare.

-- 
Best regards,
 Daniel Dekany


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