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XML::PatAct::ToObjects(3pm) |
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XML::PatAct::ToObjects − An action module for creating Perl objects
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 );
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.
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] } );
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It’d be nice if patterns could be applied even in −as−string and −grove. | ||
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Implement Perl code actions. | ||
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−as−xml to write XML into the field. |
Ken MacLeod, ken@bitsko.slc.ut.us
perl(1), Data::Grove(3)
’’Using PatAct Modules’’ and ’’Creating PatAct Modules’’ in libxml−perl.
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XML::PatAct::ToObjects(3pm) | |