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

If 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 XML::Parser is recommended, but XML::Smart::Parser will work fine too.

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

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.

Where can I learn about XML?

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

  $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...

How XML::Smart works?

  $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 XML::Smart does.

For 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 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 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 ;

But note that 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!

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

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

  ## or better:

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

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