Ubuntu Manpage: XML::PatAct::ToObjects - An action module for creating Perl objects

NAME

       XML::PatAct::ToObjects - An action module for creating Perl objects

SYNOPSIS

        use XML::PatAct::ToObjects;

        my $patterns = [ PATTERN => [ OPTIONS ],
                         PATTERN => "PERL-CODE",
                         ... ];

        my $matcher = XML::PatAct::ToObjects->new( Patterns => $patterns,
                                                   Matcher => $matcher,
                                                   CopyId => 1,
                                                   CopyAttributes => 1 );

DESCRIPTION

XML::PatAct::ToObjects is a PerlSAX handler for applying pattern-action lists to XML
parses or trees. XML::PatAct::ToObjects creates Perl objects of the types and contents of
the action items you define.

New XML::PatAct::ToObject instances are creating by calling `new()'. Parameters can be
passed as a list of key, value pairs or a hash. `new()' requires the Patterns and Matcher
parameters, the rest are optional:

Patterns
The pattern-action list to apply.

Matcher
An instance of the pattern or query matching module.

CopyId
Causes the `ID' attribute, if any, in a source XML element to be copied to an `ID'
attribute in newly created objects. Note that IDs may be lost of no pattern matches
that element or an object is not created ("-make") for that element.

CopyAttributes
Causes all attributes of the element to be copied to the newly created objects.

Each action can either be a list of options defined below or a string containing a
fragment of Perl code. If the action is a string of Perl code then simple then some
simple substitutions are made as described further below.

Options that can be used in an action item containing an option-list:

-holder
Ignore this element, but continue processing it's children (compare to -ignore).
"-pcdata" may be used with this option.

-ignore
Ignore (discard) this element and it's children (compare to -holder).

-pcdata
Character data in this element should be copied to the "Contents" field.

-make PACKAGE
Create an object blessed into PACKAGE, and continue processing this element and it's
children. PACKAGE may be the type `"HASH"' to simply create an anonyous hash.

-args ARGUMENTS
Use ARGUMENTS in creating the object specified by -make. This is commonly used to
copy element attributes into fields in the newly created object. For example:

-make => 'HASH', -args => 'URL => %{href}'

would copy the `"href"' attribute in an element to the `"URL"' field of the newly
created hash.

-field FIELD
Store this element, object, or children of this element in the parent object's field
named by FIELD.

-push-field FIELD
Similar to -field, except that FIELD is an array and the contents are pushed onto that
array.

-value VALUE
Use VALUE as a literal value to store in FIELD, otherwise ignoring this element and
it's children. Only valid with -field or -push-field. `"%{ATTRIBUTE}"' notation can
be used to substitute the value of an attribute into the literal value.

-as-string
Convert the contents of this element to a string (as in "XML::Grove::AsString") and
store in FIELD. Only valid with -field or -push-field.

-grove
Copy this element to FIELD without further processing. The element can then be
processed later as the Perl objects are manipulated. Only valid with -field or
-push-field. If ToObjects is used with PerlSAX, this will use XML::Grove::Builder to
build the grove element.

-grove-contents
Used with -make, -grove-contents creates an object but then takes all of the content
of that element and stores it in Contents.

If an action item is a string, that string is treated as a fragment of Perl code. The
following simple substitutions are performed on the fragment to provide easy access to the
information being converted:

@ELEM@
The object that caused this action to be called. If ToObjects is used with PerlSAX
this will be a hash with the element name and attributes, with XML::Grove this will be
the element object, with Data::Grove it will be the matching object, and with XML::DOM
it will be an XML::DOM::Element.

EXAMPLE

       The example pattern-action list below will convert the following XML representing a
       Database schema:

           <schema>
             <table>
               <name>MyTable</name>
               <summary>A short summary</summary>
               <description>A long description that may
                 contain a subset of HTML</description>
               <column>
                 <name>MyColumn1</name>
                 <summary>A short summary</summary>
                 <description>A long description</description>
                 <unique/>
                 <non-null/>
                 <default>42</default>
               </column>
             </table>
           </schema>

       into Perl objects looking like:

           [
             { Name => "MyTable",
               Summary => "A short summary",
               Description => $grove_object,
               Columns => [
                 { Name => "MyColumn1",
                   Summary => "A short summary",
                   Description => $grove_object,
                   Unique => 1,
                   NonNull => 1,
                   Default => 42
                 }
               ]
             }
           ]

       Here is a Perl script and pattern-action list that will perform the conversion using the
       simple name matching pattern module XML::PatAct::MatchName.  The script accepts a Schema
       XML file as an argument ($ARGV[0]) to the script.  This script creates a grove as one of
       it's objects, so it requires the XML::Grove module.

           use XML::Parser::PerlSAX;
           use XML::PatAct::MatchName;
           use XML::PatAct::ToObjects;

           my $patterns = [
             'schema'      => [ qw{ -holder                                  } ],
             'table'       => [ qw{ -make Schema::Table                      } ],
             'name'        => [ qw{ -field Name -as-string                   } ],
             'summary'     => [ qw{ -field Summary -as-string                } ],
             'description' => [ qw{ -field Description -grove                } ],
             'column'      => [ qw{ -make Schema::Column -push-field Columns } ],
             'unique'      => [ qw{ -field Unique -value 1                   } ],
             'non-null'    => [ qw{ -field NonNull -value 1                  } ],
             'default'     => [ qw{ -field Default -as-string                } ],
           ];

           my $matcher = XML::PatAct::MatchName->new( Patterns => $patterns );
           my $handler = XML::PatAct::ToObjects->new( Patterns => $patterns,
                                                      Matcher => $matcher);

           my $parser = XML::Parser::PerlSAX->new( Handler => $handler );
           my $schema = $parser->parse(Source => { SystemId => $ARGV[0] } );

TODO

       •   It'd be nice if patterns could be applied even in -as-string and -grove.

       •   Implement Perl code actions.

       •   -as-xml to write XML into the field.

AUTHOR