perl bless function Post: 302307837

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Top Forums UNIX for Dummies Questions & Answers perl bless function Post 302307837 by cbkihong on Thursday 16th of April 2009 12:01:26 PM

04-16-2009

Registered User

Quote:

Originally Posted by zedex

hi
i am not getting what exactly bless function do in perl explanation in perldoc is not very clear i tried to search on google but i am getting confused or rather not getting at all. can anybody explain in short what it does in following example as well as in general ?

Code:

sub new {
        my $class                               = shift; #1
        my $self = {}; #2
        bless ($self, $class); #3
}

The bless() function turns a vanilla reference (that can be virtually any type of reference, although hash reference is used most of the time) into an object. Without bless(), you are not doing object-oriented programming in Perl.

The first line captures the package name. If one calls

Code:

my $obj = Some::Package->new();

(1) The package name "Some::Package" will be passed as the first argument if the arrow -> is used. I forgot exactly which manpage mentioned this, but it should be there.

(2) You just create a reference type that holds the model of the object. However, the object itself has not been created yet.

(3) This is what creates the object. The reference (model) is associated with the given package name, so making the resulting object an instance of that package. (In OOP, objects are instances of a package/class/module).

It looks bizarre, but that's the way Perl objects work.

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LEARN ABOUT OSX

pod::simple::linksection

Pod::Simple::LinkSection(3pm)				 Perl Programmers Reference Guide			     Pod::Simple::LinkSection(3pm)

NAME

       Pod::Simple::LinkSection -- represent "section" attributes of L codes

SYNOPSIS

	# a long story

DESCRIPTION

       This class is not of interest to general users.

       Pod::Simple uses this class for representing the value of the "section" attribute of "L" start-element events.  Most applications can just
       use the normal stringification of objects of this class; they stringify to just the text content of the section, such as "foo" for
       "L<Stuff/foo>", and "bar" for "L<Stuff/bI<ar>>".

       However, anyone particularly interested in getting the full value of the treelet, can just traverse the content of the treeleet
       @$treelet_object.  To wit:

	 % perl -MData::Dumper -e
	   "use base qw(Pod::Simple::Methody);
	    sub start_L { print Dumper($_[1]{'section'} ) }
	    __PACKAGE__->new->parse_string_document('=head1 L<Foo/bI<ar>baz>>')
	   "
       Output:
	 $VAR1 = bless( [
			  '',
			  {},
			  'b',
			  bless( [
				   'I',
				   {},
				   'ar'
				 ], 'Pod::Simple::LinkSection' ),
			  'baz'
			], 'Pod::Simple::LinkSection' );

       But stringify it and you get just the text content:

	 % perl -MData::Dumper -e
	   "use base qw(Pod::Simple::Methody);
	    sub start_L { print Dumper( '' . $_[1]{'section'} ) }
	    __PACKAGE__->new->parse_string_document('=head1 L<Foo/bI<ar>baz>>')
	   "
       Output:
	 $VAR1 = 'barbaz';

SEE ALSO

       Pod::Simple

SUPPORT

       Questions or discussion about POD and Pod::Simple should be sent to the pod-people@perl.org mail list. Send an empty email to
       pod-people-subscribe@perl.org to subscribe.

       This module is managed in an open GitHub repository, http://github.com/theory/pod-simple/ <http://github.com/theory/pod-simple/>. Feel free
       to fork and contribute, or to clone git://github.com/theory/pod-simple.git <git://github.com/theory/pod-simple.git> and send patches!

       Patches against Pod::Simple are welcome. Please send bug reports to <bug-pod-simple@rt.cpan.org>.

COPYRIGHT AND DISCLAIMERS

       Copyright (c) 2004 Sean M. Burke.

       This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself.

       This program is distributed in the hope that it will be useful, but without any warranty; without even the implied warranty of
       merchantability or fitness for a particular purpose.

AUTHOR

       Pod::Simple was created by Sean M. Burke <sburke@cpan.org>.  But don't bother him, he's retired.

       Pod::Simple is maintained by:

       o   Allison Randal "allison@perl.org"

       o   Hans Dieter Pearcey "hdp@cpan.org"

       o   David E. Wheeler "dwheeler@cpan.org"

perl v5.16.2							    2012-10-25					     Pod::Simple::LinkSection(3pm)