[Zope] Getting error assigning sequence-item to REQUEST

[Tres Seaver]

Richard Moon <richard@dcs.co.uk> wrote:
> 
> Can anyone tell me why the following
> <dtml-in "_.string.split(tune_name,'|')">
>      <dtml-if sequence-start>
>        <dtml-call expr="REQUEST.set('tune_name',sequence-item)">
> 
> raises the error "Error Type: Name Error  Error Value:sequence"
> 
> It is the last line which raises the error.
> 
> This is the error I would expect if I was trying to use a variable which
> wasn't in the current namespace so I am confused why I cannot use
> sequence-item in this way.
> 
> Can anyone tell me the correct syntax (and why ) ?

Inside 'expr="..."', you are speaking Python, and the sequence variables,
which have names which are illegal as Python identifiers, cannot be referenced
directly.

The correct syntax would be::

 <dtml-in "_.string.split(tune_name,'|')">
      <dtml-if sequence-start>
        <dtml-call expr="REQUEST.set('tune_name',_['sequence-item'])">

which uses the "_" variable representing the current namespace.  An
alternative is to use <dtml-let> to alias the sequence variables, like so::

 <dtml-in "_.string.split(tune_name,'|')">
   <dtml-let si=sequence-item>
      <dtml-if sequence-start>
        <dtml-call expr="REQUEST.set('tune_name',si)">

This oddness is an historical artefact:  the sequence variables got their
names long before DTML got the expr="" syntax.  There is a proposal in the
DTML wiki (look under http://www.zope.org/WikiCentral to find it) to add
syntax to the <dtml-in> tag which will make all this unnecessary.

Hope that helps,

Tres.
-- 
=========================================================
Tres Seaver  tseaver@digicool.com   tseaver@palladion.com