kevind0718 has asked for the wisdom of the Perl Monks concerning the following question:

Dear Wise and Kind Monks:

The code below is mis-behaving when it does not find the XML element it is looking for.
If I look for "IssuerCountry" the correct customBucketValue is returned.

However, if I look for "SandPRating" which is not contained in the customBucketList, the code mis-behaves. In this case @rtnVal returned is defined. I would expect it to be undefined. The code does not do the assignment to @rtnVal so I would expect @rtnVal to be undefined.

many thanks for your kind assistance

kd 

sub  getCBLValue  {
  my ($cblIn, $cbNameIn);
  my  @cdn  =  undef;
  my  $textEl  =  undef;
  my  @rtnVal = undef;    # return the CustomBucketValue element

  #** ** ** ** ** ** ** ** ** 
  #  pass in the customBucketList and the name of the 
  #  dimension to look for
  ($cblIn, $cbNameIn)  = @_;
  
  foreach my $cb ( $cblIn->getChildNodes() ) {
    if ($cb->getNodeType() == ELEMENT_NODE  &&
        $cb->getNodeName()  eq  'customBucket'  )  {
       
      print '$cb node name:  ' .$cb->getNodeName()  . '  type:  '  . n
+odeTypeText($cb->getNodeType() )   .  "\n";
      #scanner( $cb ); 
    
      @cdn  =  $cb->getElementsByTagName("customDimensionName", 0);
      #print scalar @cdn;
      $textEl  =  $cdn[0]->getFirstChild();
      if ( $textEl->getData()  eq  $cbNameIn )  {
        print "\n Assignment to rtnVal ";
        @rtnVal = $cb->getElementsByTagName("customBucketValue", 0);
        last;
      }  
      
    }  # if customBucket node  
  
  }  # foreach
  print "\n  Return from  getCBLValue: " ;
  print   ( defined(@rtnVal) ?  " defined  \n" :  " undefined \n" );
  return @rtnVal; 


}  # getCBLValue

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given a node that contains XML like the following: 
<customBucketList>
<customBucket>
<customDimensionName>GSEC_SecuritySubType</customDimensionName>
<customBucketValue>1041</customBucketValue>
</customBucket>
<customBucket>
<customDimensionName>IssuerCountryOfDomicile</customDimensionName>
<customBucketValue>US</customBucketValue>
</customBucket>
<customBucket>
<customDimensionName>icbSubSector</customDimensionName>
<customBucketValue>Banks</customBucketValue>
</customBucket>
<customBucket>
</customBucketList>

[download]


Replies are listed 'Best First'.
Re: defined or undef
by ikegami (Patriarch) on Oct 30, 2007 at 14:54 UTC

    defined is not meant to be used on arrays and must not be used on arrays in forward-compatible code. It doesn't do anything meaningful.

    There's some uncertainty as to what you are trying to do.

    • Are you trying to return a list (0 or more items)? If so, you probably want to count the number of elements in the array.

      print("Number of elements: ", scalar(@rtnVal), "\n");

      [download]

      That will reveal that you do have a bug.
      my @rtnVal = undef;
      should be
      my @rtnVal = ();
      or just
      my @rtnVal = undef;

    • Are you trying to return a scalar (1 item or undefined)? If so, you shouldn't be using an array. In fact, your code actually behaves as if @rtnVal is a scalar. If you change it to a scalar $rtnVal, you should get the results you were expecting.

    Update: Added second bullet.

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[d/l]
      I am attempting to return a list, because getElementsByTagName retruns a list. In this case the list sould contain one item.

      my @rtnVal = undef;
      is adding an undefined element to the @rtnVal array? Oh my. Not what I expected.

      Is this valid code
      print ( @rtnVal ? " defined \n" : " undefined \n" );

      Please take a look at your suggested code. I do believe that your second suggestion is what I have.

      thanks for your quick reply.

      kd
[reply]

        Undefined is a special *scalar* value. It makes no sense to call an array undefined, so that should read
        print ( @rtnVal ? " not empty \n" : " empty \n" );

        Whether getElementsByTagName returns an list or not is irrelevant. I was asking what did you want getCBLValue to return.

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Re: defined or undef
by Jenda (Abbot) on Oct 31, 2007 at 21:07 UTC

    Are you sure you are using the right module? The DOM objects look ... erm ... rather inconvenient to me. Assuming you parsed the XML using XML::Rules and used these rules: 

       ...,
   'customDimensionName,customBucketValue' => 'content',
   'customBucket' => sub { '@'.$_[1]->{customDimensionName} => $_[1]->
+{customBucketValue} },
   'customBucketList' => 'no content',
   ...

    [download]
    and already had in $cblIn a reference to the hash containing the bucket list, then getting the values would be just @{$cblIn->{$cbNameIn}}. And the memory footprint would be much smaller.

    Jenda
    Support Denmark!
    Defend the free world!

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