Re: Pass through of optional parameters

 

> -----Original Message-----
> From: [email protected] 
> [mailto:[email protected]] On 
> Behalf Of Daniel Dekany
> Sent: Wednesday, May 14, 2008 4:22 AM
> To: FreeMarker-user
> Subject: Re: [FreeMarker-user] Pass through of optional parameters
> 
> Wednesday, May 14, 2008, 10:01:00 AM, Attila Szegedi wrote:
> 
> > *Sigh*. No, you can't do it, as FreeMarker mandates that all 
> > expressions used as arguments to a macro invocation resolve to a 
> > defined value. I wish we'd change that, at least for 
> optional arguments.
> >
> > Jonathan, Daniel - opinions?
> 
> I my un-implemented language there is, shown with FTL syntax:
> 
>   <@theMacro theParam!noarg>
> 
> So, there was special value (special like null is) that means 
> that the parameter (or list/map item!) is omitted. Overly 
> smart, one could say... but also quite useful. But it still 
> doesn't solve that the user has requested in this thread. The 
> thing is, if you do know that a variable potentially missing, 
> you have to indicate that in the source code everywhere you 
> refer to that variable; it has trivial maintainability 
> related reasons, so I'm reluctant to give it up.

In my case, if I get to a point where I want to use the optional
variable and it's not there, it's a bug (either in the template or the
input) and dieing horribly is an acceptable response.

> I don't see 
> how could it be a reason to relieve this rule that the 
> variable reference happens to be used as a parameter. Now, in 
> the case of FreeMarker 2.3, the problem is, that even if the 
> user accepts this philosophy of strictness, he simply can't 
> indicate that "I know this variable is possibly missing, and 
> in that case please consider the whole parameter being 
> omitted". But starting from FreeMarker 2.4, you can write 
> theParam?null. 

What's the timeline for 2.4 being released?

> It's a dirty solution, as it doesn't exactly 
> behave as if the parameter were omitted, but practically it 
> will be OK on the quality standard where FreeMarker lives.
> 

It will certainly work well enough for me.

Troy

> > Attila.
> >
> > On 2008.05.13., at 20:53, Troy Daniels wrote:
> >
> >>>
> >>> I have a macro with an optional parameter:
> >>>
> >>> <#macro term source result op context optional...>
> >>>    do stuff, possibly using ${optional.root} </#macro>
> >>>
> >>> This is called indirectly by another macro.
> >>>
> >>> <@indirectCall root=someValue />
> >>>
> >>> <#macro indirectCall optional... > stuff <@term source=s result=r 
> >>> op=o context=c ???/> </#macro>
> >>>
> >>> I'd like to pass through the optional parameter when it's 
> given to 
> >>> indirect.  At the moment, the best way that I can see to 
> do that is
> >>>
> >>> <#macro indirectCall optional... >
> >>>  stuff
> >>>  <#if optional.root??>
> >>>     <@term source=s result=r op=o context=c 
> root=optional.root />  
> >>> <#else
> >>>     <@term source=s result=r op=o context=c  />  </#if> </#macro
> >>>
> >>> Is there a more concise way of doing this?  I tried <@term {other 
> >>> args} optional=optional>, but that just meant that the 
> optional map 
> >>> in @term had a key called optional, pointing to the map I 
> wanted it 
> >>> to be.
> >>>
> >>> I can write it like this, but it rather clutters macros 
> that aren't 
> >>> trying to do anything except convey the optional parameters down.
> >>> It'll get even more cluttered if I add a second optional 
> parameter.
> >>>
> >>> Troy
> >>
> >>
> >> Also, does anyone know if the
> >> [email protected] address is active?  I 
> >> tried posting this from my work account (which receives 
> messages just 
> >> fine) but I got a bounce message like I wasn't subscribed.  I sent 
> >> mail there asking about the problem, but I haven't heard back from 
> >> it.
> 
> --
> Best regards,
>  Daniel Dekany
> 
> 
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