[Zope] neted dtml-in and ZSQL methods

[jpenny@universal-fasteners.com]

Suppose, you have a database, items,  that has fields product and scheme.

You are processing a form that has field old_product and new_product.

You have a ZSQL method, get_scheme, with parameter old_product and body
select * from items where product = <dtml-sqlvar old_product type=string>.

You also have a ZSQL method, new_scheme, with parameter new_product and
scheme.

Observation:

<dtml-in get_scheme>
     <dtml-call new_scheme>
</dtml-in>

fails, with message

          Zope Error

          Zope has encountered an error while publishing this resource. 

          Error Type: NameError
          Error Value: scheme



          Troubleshooting Suggestions

               This resource may be trying to reference a nonexistent object or variable scheme. 
               The URL may be incorrect. 
               The parameters passed to this resource may be incorrect. 
               A resource that this resource relies on may be encountering an error. 

          For more detailed information about the error, please refer to the HTML source for this page. 

          If the error persists please contact the site maintainer. Thank you for your patience. 

even though

<dtml-in get_scheme>
     <dtml-var "scheme">
</dtml-in>

prints the expected value.

Why?

Jim Penny