


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


NAME
       UNIVERSAL - 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.

           o       "VAL" is a reference blessed into either pack-
                   age "TYPE" or a package which inherits from
                   package "TYPE".





2000-04-06                 perl v5.6.1                          1





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


           o       "VAL" is a reference to a "TYPE" of Perl vari-
                   able (e.g. 'HASH').

           o       "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 sub-
           routine.   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 UNIVERSAL qw(...)".  If you want simple local access
       to them you can do

         *isa = \&UNIVERSAL::isa;

       to import isa into your package.






































2000-04-06                 perl v5.6.1                          2


