Re: Passing data to XML::Twig twig_roots callbacks....?

Ahh.. I left out one more case that I tried, not that it should
matter since $self is a ref anyway:

sub get_grandchild_info {
  my hash_ref = shift();
  return sub {
    my ($twig, $element) = @_;
    #blah blah, do something print-y here
  }
}

my $xmltwigobj = XML::Twig->new(
     twig_roots => {
       'Information/Child/Grandchild' =>
       get_grandchild_info(\$self),
     }
);

-d

Dustin Suchter wrote:
> So this code runs, but obviously doesn't pass my data. It loops the
> expected number of times, given the XML it is parsing:
> 
> sub get_grandchild_info {
>   my hash_ref = shift();
>   return sub {
>     my ($twig, $element) = @_;
>     #blah blah, do something print-y here
>   }
> }
> 
> my $xmltwigobj = XML::Twig->new(
>      twig_roots => {
>        'Information/Child/Grandchild' =>
>        get_grandchild_info,
>      }
> );
> 
> If I change the object instantiation code to what immediately
> follows, my subroutine executes precisely 1 time only:
> 
> sub get_grandchild_info {
>   my hash_ref = shift();
>   return sub {
>     my ($twig, $element) = @_;
>     #blah blah, do something print-y here
>   }
> }
> 
> my $xmltwigobj = XML::Twig->new(
>      twig_roots => {
>        'Information/Child/Grandchild' =>
>        get_grandchild_info(),
>      }
> );
> 
> And finally this version does the same thing, executing just the
> first time the subroutine is "instantiated" - a term I'll use
> lightly since I believe this is technically a closure-utilizing
> callback, not an object:
> 
> sub get_grandchild_info {
>   my hash_ref = shift();
>   return sub {
>     my ($twig, $element) = @_;
>     #blah blah, do something print-y here
>   }
> }
> 
> my $xmltwigobj = XML::Twig->new(
>      twig_roots => {
>        'Information/Child/Grandchild' =>
>        get_grandchild_info($self),
>      }
> );
> 
> I'm guessing there's something wrong with the prototype for my
> subroutine so $smltwigobj isn't really connecting with
> get_granchild_info when I change the number of args... the question
> is (a) why? and (b) how to fix that?
> 
> 
> Jenda Krynicky wrote:
>> From: Dustin Suchter <[email protected]>
>>> I'm having a hard time wrapping my brain around the idea of using
>>> twig_roots with twig_handlers (specifically so I can pass data back
>>> and forth) in order to process large XML files. Perhaps I'm missing
>>> something obvious, and hopefully someone can help!
>>>
>>> I've got a large XML file currently parsed cleanly using twig_roots
>>> and setting callbacks on various elements:
>>>
>>> my $xmltwigobj = XML::Twig->new(
>>>     twig_roots => {
>>>         'Information/Child/Grandchild' => \&get_grandchild_info,
>>>     }
>>> );
>>>
>>> sub get_grandchild_info {
>>>     my ($twig, $element) = @_;
>>>     #blah blah, do something print-y here
>>> }
>>>
>>> My problem is that I'd like to store the info I parse via
>>> get_grandchild_info somewhere useful, where "useful" is not (a) in a
>>> global or (b) printed somewhere. Specifically, I'd like to pass the
>>> reference to a DBM::Deep object to get_grandchild_info and have any
>>> new info added to the existing DBM::Deep object, but really we
>>> shouldn't need to be specific, I just want something like:
>>>
>>> sub get_grandchild_info_extra {
>>>     my ($twig, $element, $hash_ref) = @_;
>>>     #awesomeness
>>> }
>>>
>>> I found Question 27 at
>>> http://xmltwig.com/xmltwig/XML-Twig-FAQ.html#Q27 to be pretty spot-on
>>> for my needs in terms of data passing, but in the end it didn't help
>>> me since nobody seems to use the twig_roots parsing methodology in
>>> combination with the 'closures' mentioned there (which smell a lot
>>> like globals to me anyway...).
>>>
>>> I'd love to see an example of how to modify my code, above, to allow
>>> me to pass a 3rd argument to my callback subroutine.
>> sub get_grandchild_info {
>> 	my hash_ref = shift();
>> 	return sub {
>>      my ($twig, $element) = @_;
>>      #blah blah, do something print-y here
>>    }
>> }
>>
>> ...
>>
>> my $xmltwigobj = XML::Twig->new(
>>     twig_roots => {
>>         'Information/Child/Grandchild' => 
>> get_grandchild_info(\%DBM_HASH),
>>     }
>> );
>>
>>
>>
>> Sometimes a plain old global is the best solution though.
>>
>> And sometimes it's better to have a look at a different module. Maybe 
>> XML::Rules will end up being easier. Though that of course depends on 
>> your XML and your needs.
>>
>> XML::Rules will take care of remembering the data for you and if you 
>> like you can instruct it to store the data of some tag in a DBM::Deep 
>> hash:
>>
>>
>> use XML::Rules;
>> use DBM::Deep;
>>
>> my $parser = XML::Rules->new(
>> 	start_rules => [
>> 		YourHugeTag => sub {
>> 			my %temp = %{$_[1]};
>> 			tie %{$_[1]}, 'DBM::Deep', $filename;
>> 			%{$_[1]} = %temp;
>> 			1;
>> 		}
>> 	],
>> 	rules => [
>> 		...
>>
>> (or if the tag doesn't have any attributes you'd be interested in
>>
>>
>> my $parser = XML::Rules->new(
>> 	start_rules => [
>> 		YourHugeTag => sub {
>> 			tie %{$_[1]}, 'DBM::Deep', $filename;
>> 			# and maybe 
>> 			# %{$_[1]} = (); 
>> 			# to clear the hash
>> 			1;
>> 		}
>> 	],
>> 	rules => [
>> 		...
>>
>> And now all the data returned by the rules specified for the child 
>> tabs of YourHugeTag  will be stored in the DBM::Deep and be available 
>> in $_[1] within the rule specified for YourHugeTag.
>>
>>
>> Jenda 
>> ===== [email protected] === http://Jenda.Krynicky.cz =====
>> When it comes to wine, women and song, wizards are allowed 
>> to get drunk and croon as much as they like.
>> 	-- Terry Pratchett in Sourcery
>>
>> _______________________________________________
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> 
> 
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