[1.6 bug] Using self/parent/parent for detecting where one is in the document hierarchy

[Chris Croome]

Hi

If some functionality is needed based on where one is in the document
hierarchy then using things like this mostly works:

  petal:condition="true:  self/parent/parent;
                   true:  self/parent/parent/children"

Or:

  petal:condition="false: self/parent/parent/equals ancestor;"

But if a document doesn't exist when testing for a parent/parent (for
example when a template designed for grandchild pages is used for child
pages) then there is an internal server error rather than Petal
returning false and things like this are written to the apache logs:

  [PETAL ERROR] Cannot find value for 'equals' at '/self/parent/parent':
  equals cannot be retrieved
  (current value was undef, near self/parent/parent/equals ancestor) at
  /usr/lib/perl5/site_perl/5.8.6/Petal/Hash/Var.pm line 125

Which is rather inconvient...

Chris

--
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web design                             http://www.webarchitects.co.uk/ 
web content management                               http://mkdoc.com/   
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[Bruno Postle-2]

>  [PETAL ERROR] Cannot find value for 'equals' at
>  '/self/parent/parent': equals cannot be retrieved (current value
>  was undef, near self/parent/parent/equals ancestor) at
>  /usr/lib/perl5/site_perl/5.8.6/Petal/Hash/Var.pm line 125

If self/parent doesn't return a document, then calling a method on
this non-object can't possibly work.

Test for the existence of self/parent first:

  <h1 petal:condition="self/parent">
    This document has a parent called
    <span petal:replace="self/parent/title">Mavis</span>
  </h1>

  <h1 petal:condition="self/parent; self/parent/parent">
    This document has a grandparent called
    <span petal:replace="self/parent/parent/title">Betty</span>
  </h1>

  <h1 petal:condition="false: self/parent">
    This document doesn't have a parent :-(
  </h1>

  <h1 petal:condition="self/parent; false: self/parent/parent">
    This document doesn't have a grandparent :-(
  </h1>

--
Bruno
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[Chris Croome]

Hi

On Fri 24-Feb-2006 at 12:48:23PM +0000, Bruno Postle wrote:

>
> Test for the existence of self/parent first:
>
>  <h1 petal:condition="self/parent">
>    This document has a parent called
>    <span petal:replace="self/parent/title">Mavis</span>
>  </h1>
>
>  <h1 petal:condition="self/parent; self/parent/parent">
>    This document has a grandparent called
>    <span petal:replace="self/parent/parent/title">Betty</span>
>  </h1>
>
>  <h1 petal:condition="false: self/parent">
>    This document doesn't have a parent :-(
>  </h1>
>
>  <h1 petal:condition="self/parent; false: self/parent/parent">
>    This document doesn't have a grandparent :-(
>  </h1>

I know this should work but it doesn't seem to -- for example try this
code in a document:

  <!--? document location test code -->
    <!--? root document -->
      <div
        petal:condition="false: self/parent;"
      >
        This document has no parent therefore it must be the front page.
      </div>
    <!--? child document -->
      <div
        petal:condition="true:  self/parent;
                         false: self/parent/parent;"
      >
        This document has a parent but no grand parent, therfore
        it must be a child of the front page document.
      </div>
    <!--? grandchild document -->
      <div
        petal:condition="true:  self/parent/parent;
                         false: self/parent/parent/parent;"
      >
        This document has a parent and a grand parent, therfore
        it must be a grandchild of the front page document.
      </div>
    <!--? great grandchild document -->
      <div
        petal:condition="true:  self/parent/parent/parent;
                         false: self/parent/parent/parent/parent;"
      >
        This document has a parent and a grand parent and a great
        grandparent, therefore it must be a great grandchild of
        the front page document.
      </div>
    <!--? great great grandchild document -->
      <div
        petal:condition="true:  self/parent/parent/parent/parent;
                         false: self/parent/parent/parent/parent/parent;"
      >
        This document has a parent and a grand parent and a great
        grandparent and a great great grandperent, therefore it must
        be a great great grandchild of the front page document.
      </div>

I get a internal server error and this error in the logs when this is
added to a template that is a child of the front page:

  [PETAL ERROR] Cannot find value for 'parent' at '/self/parent/parent': parent cannot be retrieved

Chris

--
Chris Croome                               <chris@...>
web design                             http://www.webarchitects.co.uk/ 
web content management                               http://mkdoc.com/   
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[Bruno Postle-2]

Chris Croome wrote:
>
> I know this should work but it doesn't seem to -- for example try this
> code in a document:

Re-read my email.

If an object or document possibly doesn't exist, you have to test
for its existence before trying to access methods.

This assumes that self/parent exists:

   <div
   petal:condition="true:  self/parent/parent;
                    false: self/parent/parent/parent;"
   >

This code makes no assumptions:

   <div
   petal:condition="true:  self/parent;
                    true:  self/parent/parent;
                    false: self/parent/parent/parent;"
   >

--
Bruno
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