universal::can(3) [centos man page]

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 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 v5.16.3							    2012-07-26							 UNIVERSAL::can(3)

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UNIVERSAL::require(3)					User Contributed Perl Documentation				     UNIVERSAL::require(3)

NAME

       UNIVERSAL::require - require() modules from a variable

SYNOPSIS

	 # This only needs to be said once in your program.
	 require UNIVERSAL::require;

	 # Same as "require Some::Module"
	 my $module = 'Some::Module';
	 $module->require or die $@;

	 # Same as "use Some::Module"
	 BEGIN { $module->use or die $@ }

DESCRIPTION

       If you've ever had to do this...

	   eval "require $module";

       to get around the bareword caveats on require(), this module is for you.  It creates a universal require() class method that will work with
       every Perl module and its secure.  So instead of doing some arcane eval() work, you can do this:

	   $module->require;

       It doesn't save you much typing, but it'll make alot more sense to someone who's not a ninth level Perl acolyte.

Methods
       require

	 my $return_val = $module->require	     or die $@;
	 my $return_val = $module->require($version) or die $@;

       This works exactly like Perl's require, except without the bareword restriction, and it doesn't die.  Since require() is placed in the
       UNIVERSAL namespace, it will work on any module.  You just have to use UNIVERSAL::require somewhere in your code.

       Should the module require fail, or not be a high enough $version, it will simply return false and not die.  The error will be in $@ as well
       as $UNIVERSAL::require::ERROR.

	   $module->require or die $@;

       use

	   my $require_return = $module->use	       or die $@;
	   my $require_return = $module->use(@imports) or die $@;

       Like "UNIVERSAL::require", this allows you to "use" a $module without having to eval to work around the bareword requirement.  It returns
       the same as require.

       Should either the require or the import fail it will return false.  The error will be in $@.

       If possible, call this inside a BEGIN block to emulate a normal "use" as closely as possible.

	   BEGIN { $module->use }

SECURITY NOTES

       UNIVERSAL::require makes use of "eval STRING".  In previous versions of UNIVERSAL::require it was discovered that one could craft a class
       name which would result in code being executed.	This hole has been closed.  The only variables now exposed to "eval STRING" are the
       caller's package, filename and line which are not tainted.

       UNIVERSAL::require is taint clean.

COPYRIGHT

       Copyright 2001, 2005 by Michael G Schwern <schwern@pobox.com>.

       This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.

       See http://www.perl.com/perl/misc/Artistic.html

AUTHOR

       Michael G Schwern <schwern@pobox.com>

       Now maintained by Neil Bowers (NEILB).

SEE ALSO

       Module::Load,  "require" in perlfunc, <http://dev.perl.org/rfc/253.pod>

perl v5.18.2							    2013-09-27						     UNIVERSAL::require(3)

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