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 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 - 2014, chromatic. This module is made available under the
same terms as Perl 5.12.