[FreeMarker-user] How to check whether it's an empty string macro param ?

[Albert Kam]

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 ?

Thank you ..

[Daniel Dekany]

Post by Albert Kam
<#macro test param>
</#macro>
But i want the param to be optional, so, i want to put a default
<#macro test param="">
<#if notEmptyString(param)>
....
<#else>
....
</#if>
</#macro>
<#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...

Post by Albert Kam
Thank you ..