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

Check::ISA(3pm) 					User Contributed Perl Documentation					   Check::ISA(3pm)

NAME

       Check::ISA - DWIM, correct checking of an object's class

SYNOPSIS

	       use Check::ISA;

	       if ( obj($foo, "SomeClass") ) {
		       $foo->some_method;
	       }

	       # instead of one of these methods:
	       UNIVERSAL::isa($foo, "SomeClass") # WRONG
	       ref $obj eq "SomeClass"; # VERY WRONG
	       $foo->isa("SomeClass") # May die
	       local $@; eval { $foo->isa("SomeClass") } # too long

DESCRIPTION

       This module provides several functions to assist in testing whether a value is an object, and if so asking about its class.

FUNCTIONS

       obj $thing, [ $class ]
	   This function tests if $thing is an object.

	   If $class is provided, it also tests tests whether "$thing->isa($class)".

	   $thing is considered an object if it's blessed, or if it's a "GLOB" with a valid "IO" slot (the "IO" slot contains a FileHandle object
	   which is the actual invocant). This corresponds directly to "gv_fetchmethod".

       obj_does $thing, [ $class_or_role ]
	   Just like "obj" but uses "DOES" in UNIVERSAL instead of "isa" in UNIVERSAL.

	   "DOES" in UNIVERSAL is just like "isa", except it's use is encouraged to query about an interface, as opposed to the object structure.
	   If "DOES" is not overridden by th ebject, calling it is semantically identical to calling "isa".

	   This is probably reccomended over "obj" for interoperability, but can be slower on Perls before 5.10.

	   Note that "DOES" in UNIVERSAL

       inv $thing, [ $class_or_role ]
	   Just like "obj_does", but also returns true for classes.

	   Note that this method is slower, but is supposed to return true for any value you can call methods on (class, object, filehandle, etc).

	   Look into autobox if you would like to be able to call methods on all values.

       obj_can $thing, $method
       inv_can $thing, $method
	   Checks if $thing is an object or class, and calls "can" on $thing if appropriate.

SEE ALSO

       UNIVERSAL, Params::Util, autobox, Moose, asa

VERSION CONTROL

       This module is maintained using Darcs. You can get the latest version from <http://nothingmuch.woobling.org/code>, and use "darcs send" to
       commit changes.

AUTHOR

       Yuval Kogman <nothingmuch@woobling.org>

COPYRIGHT

	       Copyright (c) 2008 Yuval Kogman. All rights reserved
	       This program is free software; you can redistribute
	       it and/or modify it under the same terms as Perl itself.

perl v5.10.0							    2008-07-25							   Check::ISA(3pm)

UNIVERSAL(3pm)						 Perl Programmers Reference Guide					    UNIVERSAL(3pm)

NAME

       UNIVERSAL - base class for ALL classes (blessed references)

SYNOPSIS

	   $is_io = $fd->isa("IO::Handle");
	   $is_io = Class->isa("IO::Handle");

	   $sub = $obj->can("print");
	   $sub = Class->can("print");

	   use UNIVERSAL qw( isa can VERSION );
	   $yes = isa $ref, "HASH" ;
	   $sub = can $ref, "fandango" ;
	   $ver = VERSION $obj ;

DESCRIPTION

       "UNIVERSAL" is the base class which all bless references will inherit from, see perlobj.

       "UNIVERSAL" provides the following methods and functions:

       $obj->isa( TYPE ), CLASS->isa( TYPE ), isa( VAL, TYPE )
	       C<TYPE> is a package name
	       $obj is a blessed reference or a string containing a package name
	       C<CLASS> is a package name
	       C<VAL> is any of the above or an unblessed reference

	   When used as an instance or class method ("$obj-"isa( TYPE )>), "isa" returns true if $obj is blessed into package "TYPE" or inherits
	   from package "TYPE".

	   When used as a class method ("CLASS-"isa( TYPE )>; sometimes referred to as a static method), "isa" returns true if "CLASS" inherits
	   from (or is itself) the name of the package "TYPE" or inherits from package "TYPE".

	   When used as a function, like

	      use UNIVERSAL qw( isa ) ;
	      $yes = isa $h, "HASH";
	      $yes = isa "Foo", "Bar";

	   or

	      require UNIVERSAL ;
	      $yes = UNIVERSAL::isa $a, "ARRAY";

	   , "isa" returns true in the same cases as above and also if "VAL" is an unblessed reference to a perl variable of type "TYPE", such as
	   "HASH", "ARRAY", or "Regexp".

       $obj->can( METHOD ), CLASS->can( METHOD ), can( VAL, METHOD )
	   "can" checks if the object or class has a method called "METHOD". If it does then a reference to the sub is returned. If it does not
	   then undef is returned.  This includes methods inherited or imported by $obj, "CLASS", or "VAL".

	   "can" cannot know whether an object will be able to provide a method through AUTOLOAD, so a return value of undef does not necessarily
	   mean the object will not be able to handle the method call. To get around this some module authors use a forward declaration (see perl-
	   sub) for methods they will handle via AUTOLOAD. For such 'dummy' subs, "can" will still return a code reference, which, when called,
	   will fall through to the AUTOLOAD. If no suitable AUTOLOAD is provided, calling the coderef will cause an error.

	   "can" can be called as a class (static) method, an object method, or a function.

	   When used as a function, if "VAL" is a blessed reference or package name which has a method called "METHOD", "can" returns a reference
	   to the subroutine.  If "VAL" is not a blessed reference, or if it does not have a method "METHOD", undef is returned.

       VERSION ( [ REQUIRE ] )
	   "VERSION" will return the value of the variable $VERSION in the package the object is blessed into. If "REQUIRE" is given then it will
	   do a comparison and die if the package version is not greater than or equal to "REQUIRE".

	   "VERSION" can be called as either a class (static) method, an object method or or a function.

       These subroutines should not be imported via "use UNIVERSAL qw(...)".  If you want simple local access to them you can do

	 *isa = &UNIVERSAL::isa;

       to import isa into your package.

perl v5.8.0							    2002-06-01							    UNIVERSAL(3pm)