Rails to Grails Tips – GSP tags and Array Primitives

Interesting issue that left me scratching my head this morning…

using gsp tags, you can iterate over arrays:

   <g:each in="${myarray}">
      <p>${it.title}</p>
   </g:each>

but if you do something slightly more clever:

   <g:each in="${myarray}">
      <p><g:link action='myaction' id='${it.id}'>${it.title}</g:link></p>
   </g:each>

You’ll get null pointer exceptions.

Why?

Because the <g:link> tag creates its own instance of the special variable it inside its own ‘domain’.

Fix

add the parameter var='myvar' to the <g:each”> tag: <g:each in="${myarray}" var="myvar">. Then, use ${myvar.id} and ${myvar.title} in your code:

   <g:each in="${myarray}" var="myvar">
      <p><g:link action='myaction' id='${myvar.id}'>${myvar.title}</g:link></p>
   </g:each>

And everything should work again.