Skip site navigation (1)Skip section navigation (2)

FreeBSD Manual Pages

  
 
  

home | help
UNIVERSAL::can(3)     User Contributed Perl Documentation    UNIVERSAL::can(3)

NAME
       UNIVERSAL::can -	work around buggy code calling UNIVERSAL::can()	as a
       function

SYNOPSIS
       To use this module, simply:

	 use UNIVERSAL::can;

DESCRIPTION
       The UNIVERSAL class provides a few default methods so that all objects
       can use them.  Object orientation allows	programmers to override	these
       methods in subclasses to	provide	more specific and appropriate
       behavior.

       Some authors call methods in the	UNIVERSAL class	on potential invocants
       as functions, bypassing any possible overriding.	 This is wrong and you
       should not do it.  Unfortunately, not everyone heeds this warning and
       their bad code can break	your good code.

       This module replaces "UNIVERSAL::can()" with a method that checks to
       see if the first	argument is a valid invocant has its own "can()"
       method.	If so, it gives	a warning and calls the	overridden method,
       working around buggy code.  Otherwise, everything works as you might
       expect.

       Some people argue that you must call "UNIVERSAL::can()" as a function
       because you don't know if your proposed invocant	is a valid invocant.
       That's silly.  Use "blessed()" from Scalar::Util	if you want to check
       that the	potential invocant is an object	or call	the method anyway in
       an "eval" block and check for failure (though check the exception
       returned, as a poorly-written "can()" method could break	Liskov and
       throw an	exception other	than "You can't	call a method on this type of
       invocant").

       Just don't break	working	code.

AUTHOR
       chromatic, "<chromatic@wgz.org>"

BUGS
       Please report any bugs or feature requests to
       "bug-universal-can@rt.cpan.org",	or through the web interface at
       <http://rt.cpan.org/NoAuth/ReportBug.html?Queue=UNIVERSAL-can>.	This
       will contact me,	hold onto patches so I don't drop them,	and will
       notify you of progress on your request as I make	changes.

ACKNOWLEDGEMENTS
       Inspired	by UNIVERSAL::isa by Yuval Kogman, Autrijus Tang, and myself.

       Adam Kennedy has	tirelessly made	me tired by reporting potential	bugs
       and suggesting ideas that found actual bugs.

       Mark Clements helped to track down an invalid invocant bug.

       Curtis "Ovid" Poe finally provided the inspiration I needed to clean up
       the interface.

       Peter du	Marchie	van Voorthuysen	identified and fixed a problem with
       calling "SUPER::can".

       Daniel LeWarne found and	fixed a	deep recursion error.

       Norbert BuchmA1/4ller fixed an overloading bug in blessed invocants.

       The Perl	QA list	had a huge... discussion... which inspired my
       realization that	this module needed to do what it does now.

COPYRIGHT & LICENSE
       Copyright (c) 2005 - 2014, chromatic. This module is made available
       under the same terms as Perl 5.12.

perl v5.32.0			  2014-03-28		     UNIVERSAL::can(3)

NAME | SYNOPSIS | DESCRIPTION | AUTHOR | BUGS | ACKNOWLEDGEMENTS | COPYRIGHT & LICENSE

Want to link to this manual page? Use this URL:
<https://www.freebsd.org/cgi/man.cgi?query=UNIVERSAL::can&sektion=3&manpath=FreeBSD+12.2-RELEASE+and+Ports>

home | help