UNIVERSAL(3) Perl Programmers Reference Guide UNIVERSAL(3)NAMEUNIVERSAL - base class for ALL classes (blessed refer
ences)
SYNOPSIS
$io = $fd->isa("IO::Handle");
$sub = $obj->can('print');
$yes = UNIVERSAL::isa($ref, "HASH");
DESCRIPTION
"UNIVERSAL" is the base class which all bless references
will inherit from, see the perlobj manpage
"UNIVERSAL" provides the following methods
isa ( TYPE )
"isa" returns true if "REF" is blessed into package
"TYPE" or inherits from package "TYPE".
"isa" can be called as either a static or object
method call.
can ( METHOD )
"can" checks if the object has a method called
"METHOD". If it does then a reference to the sub is
returned. If it does not then undef is returned.
"can" can be called as either a static or object
method call.
VERSION ( [ REQUIRE ] )
"VERSION" will return the value of the variable "$VER
SION" 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 static or object
method call.
The "isa" and "can" methods can also be called as subrou
tines
UNIVERSAL::isa ( VAL, TYPE )
"isa" returns true if one of the following statements
is true.
"VAL" is a reference blessed into either pack
age "TYPE" or a package which inherits from
package "TYPE".
"VAL" is a reference to a "TYPE" of Perl vari
able (e.g. 'HASH').
"VAL" is the name of a package that inherits
from (or is itself) package "TYPE".
UNIVERSAL::can ( VAL, METHOD )
If "VAL" is a blessed reference 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.
These subroutines should not be imported via "use UNIVER
SAL qw(...)". If you want simple local access to them you
can do
*isa = \&UNIVERSAL::isa;
to import isa into your package.
2001-02-22 perl v5.6.1 UNIVERSAL(3)
