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libxml-smart-perl - Perl module for access to parsed XML trees…  more info»

FAQ.pod


=head1 NAME

XML::Smart::FAQ - Frequently Asked Questions about XML::Smart.

=head1 SYNOPSIS

This is the Frequently Asked Questions list for XML::Smart.

=head1 QUESTIONS

B<For new questions send an e-mail to the author, but please, read first all the F.A.Q.>

=head2 Do I need to install XML::Parser to can use XML::Smart?

No! XML::Smart already comes with 2 independent parsers, XML::Smart::Parser and XML::Smart::HTMLParser.

If L<XML::Parser> is found XML::Smart will use it by default, and the 2nd options will be XML::Smart::Parser.

Note that for complex parsing L<XML::Parser> is recommended, but XML::Smart::Parser will work fine too.

=head2 What is the best version of XML::Smart to install?

Is always the last! Always take a look for new versions before aks for help on XML::Smart.

Note that internally XML::Smart is complex, since the main idea of it is to remove the complexity from the hand of the programmer.
Actually the idea is to enable the Perl programmer to use and create XML data without really know the XML format.

=head2 Where can I learn about XML?

http://www.xml.com

=head2 How to apply a DTD to a XML::Smart object tree?

Take a look in the method I<apply_dtd()>. Example of use:

  $xml->apply_dtd(q`
  <!DOCTYPE cds [
  <!ELEMENT cds (album+)>
  <!ATTLIST cds
            creator  CDATA
            date     CDATA #REQUIRED
  >
  <!ELEMENT album (artist , tracks+)>
  <!ELEMENT artist (#PCDATA)>
  <!ELEMENT tracks (#PCDATA)>
  ]>
  `);

This will format automatically elements, attributes, etc...

=head2 How XML::Smart works?

To create I<XML::Smart>, first I have created the module L<Object::MultiType>.
With it you can have an object that works at the same time as a HASH, ARRAY, SCALAR,
CODE & GLOB. So you can do things like this with the same object:

  $obj = Object::MultiType->new() ;
  
  $obj->{key} ;
  $obj->[0] ;
  $obj->method ;
  
  @l = @{$obj} ;
  %h = %{$obj} ;
  
  &$obj(args) ;
  
  print $obj "send data\n" ;

Seems to be crazy, and can be more if you use tie() inside it, and this is what I<XML::Smart> does.

For I<XML::Smart>, the access in the Hash and Array way paste through tie(). In other words, you have a tied HASH
and tied ARRAY inside it. This tied Hash and Array work together, soo B<you can access a Hash key
as the index 0 of an Array, or access an index 0 as the Hash key>:

  %hash = (
  key => ['a','b','c']
  ) ;
  
  $hash->{key}    ## return $hash{key}[0]
  $hash->{key}[0] ## return $hash{key}[0]
  $hash->{key}[1] ## return $hash{key}[1]
  
  ## Inverse:
  
  %hash = ( key => 'a' ) ;
  
  $hash->{key}    ## return $hash{key}
  $hash->{key}[0] ## return $hash{key}
  $hash->{key}[1] ## return undef

The best thing of this new resource is to avoid wrong access to the data and warnings when you try to
access a Hash having an Array (and the inverse). Thing that generally make the script die().

Once having an easy access to the data, you can use the same resource to B<create> data!
For example:

  ## Previous data:
  <hosts>
    <server address="192.168.2.100" os="linux" type="conectiva" version="9.0"/>
  </hosts>
  
  ## Now you have {address} as a normal key with a string inside:
  $XML->{hosts}{server}{address}
  
  ## And to add a new address, the key {address} need to be an ARRAY ref!
  ## So, XML::Smart make the convertion: ;-P
  $XML->{hosts}{server}{address}[1] = '192.168.2.101' ;
  
  ## Adding to a list that you don't know the size:
  push(@{$XML->{hosts}{server}{address}} , '192.168.2.102') ;
  
  ## The data now:
  <hosts>
    <server os="linux" type="conectiva" version="9.0"/>
      <address>192.168.2.100</address>
      <address>192.168.2.101</address>
      <address>192.168.2.102</address>
    </server>
  </hosts>

Than after changing your XML tree using the Hash and Array resources you just
get the data remade (through the Hash tree inside the object):

  my $xmldata = $XML->data ;

B<But note that I<XML::Smart> always return an object>! Even when you get a final
key. So this actually returns another object, pointhing (inside it) to the key:

  $addr = $XML->{hosts}{server}{address}[0] ;
  
  ## Since $addr is an object you can TRY to access more data:
  $addr->{foo}{bar} ; ## This doens't make warnings! just return UNDEF.

  ## But you can use it like a normal SCALAR too:

  print "$addr\n" ;

  $addr .= ':80' ; ## After this $addr isn't an object any more, just a SCALAR!

=head2 When I generate the XML data new lines (\n) are added to the content!

You should use the options for the method data() and save() to not add identation to the generated data:

  $XML->data( noident => 1 ) ;

  ## or better:

  $XML->data( nospace => 1 ) ;

=head2 Your question is not here?

Just send me an e-mail. ;-P

=head1 AUTHOR

Graciliano M. P. <gm@virtuasites.com.br>

I will appreciate any type of feedback (include your opinions and/or suggestions). ;-P

Enjoy and thanks for who are enjoying this tool and have sent e-mails! ;-P

=head1 ePod

This document was written in L<ePod> (easy-POD), than converted to POD, and from here you know the way.

=cut

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