UNIVERSAL::isa(3) User Contributed Perl Documentation UNIVERSAL::isa(3)NAMEUNIVERSAL::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 v5.18.1 2012-07-26 UNIVERSAL::isa(3)
