NamedDTMLInLoop

Named DTML-In Loop Proposal

Jim

Note that this proposal applies to all dtml tags that introduce new variables (e.g. the tree tag).

Poster Child:

    <dtml-in SQL1 var=s1><dtml-in SQL2 var=s2>
      <dtml-if expr="s1.key == s2.key">
      <dtml-var s1/name> is the same as <dtml-var s2/name>;
      </dtml-if>
    </dtml-in></dtml-in>

Goals

• Make DTML-In variables such as sequence-item easier and more natural to use in expressions.
• Allow namespaces of nested DTML-In tags to be easily separated and separately accessed.

Proposed Changes

Add an optional argument to DTML-In which declares a loop object. This wouldn't affect the standard (sequence-item) syntax, but would add an object to the namespace through which all of the loop variables could be accessed. The attribute names of the loop object would use underscores (_) in place of hyphens.

Implement PathNameTraversal.

Result

This would allow loop variables to be distinguished by prepending the loop object name to them, with a slash (/) in DTML names or a dot (.) in expressions.

Example:

    <dtml-in first_sequence var=outer>;
      <dtml-in second_sequence var=inner>
        The following should all produce the same result:
        <dtml-var sequence-item>
        <dtml-var expr="_['sequence_item']">
        <dtml-var inner/sequence-item>
        <dtml-var expr="inner.sequence_item">
        We can also access variables from the outer loop, like so:
        <dtml-var outer/sequence-item>
        <dtml-var expr="outer.sequence_item">
      </dtml-in>
    </dtml-in>