Re: How to check whether it's an empty string macro param ?

Tuesday, July 30, 2013, 11:51:37 AM, Albert Kam wrote:

> I am currently using some macros that can accept a param, which can be string or sequence like this :
> <#macro test param>
> </#macro>
>
> But i want the param to be optional, so, i want to put a default
> value on it, and check whether the param is specified or not :
> <#macro test param="">
>     <#if notEmptyString(param)>
>         ....
>     <#else>
>         ....
>     </#if>
> </#macro>
>
> And here's my function on checking the emptiness of the param :
> <#function notEmptyString value>
>  <#return !(value?is_string) || value != "">
> </#function>
>
> Altough i havent faced any problems yet, i have my own doubts with
> this function, since the param can be of multiple types which will
> pass the ?is_string. If so, how do i do the checking correctly ?

I don't see any technical problems with that check. However, maybe
param?has_content is nicer (and much faster), assuming you can treat
"" and [] (and {}) the same.

I don't know about a trick to tell with 100% certainty if the
parameter was specified though. You could chose a value that's simply
unlikely enough to be passed in to be treated as the sign of that the
parameter was omitted. I know, ugly. We had to introduce a special
marker value that can only be used as the default of a parameter, like
`<#macro my param=.omitted><#if param?is_omitted>`, but there's no such
thing yet...

> Thank you ..

-- 
Thanks,
 Daniel Dekany


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