UNIVERSAL::can(3) User Contributed Perl Documentation UNIVERSAL::can(3)NAMEUNIVERSAL::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 Buchmueller 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 - 2011, chromatic. This module is made available
under the same terms as Perl 5.12.
POD ERRORS
Hey! The above document had some coding errors, which are explained
below:
Around line 146:
Non-ASCII character seen before =encoding in 'Buchmueller'.
Assuming UTF-8
perl v5.18.1 2012-07-26 UNIVERSAL::can(3)
