universal::isa(3pm) [debian man page]

UNIVERSAL::isa(3pm)					User Contributed Perl Documentation				       UNIVERSAL::isa(3pm)

NAME

       UNIVERSAL::isa - recover from people calling UNIVERSAL::isa as a function

SYNOPSIS

	   # from the shell
	   echo 'export PERL5OPT=-MUNIVERSAL::isa' >> /etc/profile

	   # within your program
	   use UNIVERSAL::isa;

	   # enable warnings for all dodgy uses of UNIVERSAL::isa
	   use UNIVERSAL::isa 'verbose';

DESCRIPTION

       Whenever you use "isa" in UNIVERSAL as a function, a kitten using Test::MockObject dies. Normally, the kittens would be helpless, but if
       they use UNIVERSAL::isa (the module whose docs you are reading), the kittens can live long and prosper.

       This module replaces "UNIVERSAL::isa" with a version that makes sure that, when called as a function on objects which override "isa", "isa"
       will call the appropriate method on those objects

       In all other cases, the real "UNIVERSAL::isa" gets called directly.

       NOTE: You should use this module only for debugging purposes. It does not belong as a dependency in running code.

WARNINGS

       If the lexical warnings pragma is available, this module will emit a warning for each naughty invocation of "UNIVERSAL::isa". Silence these
       warnings by saying:

	   no warnings 'UNIVERSAL::isa';

       in the lexical scope of the naughty code.

       After version 1.00, warnings only appear when naughty code calls UNIVERSAL::isa() as a function on an invocant for which there is an
       overridden isa().  These are really truly active bugs, and you should fix them rather than relying on this module to find them.

       To get warnings for all potentially dangerous uses of UNIVERSAL::isa() as a function, not a method (that is, for all uses of the method as
       a function, which are latent bugs, if not bugs that will break your code as it exists now), pass the "verbose" flag when using the module.
       This can generate many extra warnings, but they're more specific as to the actual wrong practice and they usually suggest proper fixes.

SEE ALSO

       Perl::Critic::Policy::BuiltinFunctions::ProhibitUniversalIsa

       UNIVERSAL::can for another discussion of the problem at hand.

       Test::MockObject for one example of a module that really needs to override "isa()".

       Any decent explanation of OO to understand why calling methods as functions is a staggeringly bad idea.

AUTHORS

       Audrey Tang <cpan@audreyt.org>

       chromatic <chromatic@wgz.org>

       Yuval Kogman <nothingmuch@woobling.org>

COPYRIGHT &; LICENSE
       Copyright (c) 2005 - 2011, chromatic. This module is made available under the same terms as Perl 5.12.

perl v5.14.2							    2012-04-18						       UNIVERSAL::isa(3pm)

UNIVERSAL::can(3pm)					User Contributed Perl Documentation				       UNIVERSAL::can(3pm)

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 <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 BuchmA~Xller 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
       Artistic License 2.0, copyright (c) 2005 - 2011 chromatic. Some rights reserved.

perl v5.12.3							    2011-06-13						       UNIVERSAL::can(3pm)