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



NAME
       base - Establish an ISA relationship with base classes at compile time

SYNOPSIS
           package Baz;
           use base qw(Foo Bar);

DESCRIPTION
       Unless you are using the "fields" pragma, consider this module discouraged in favor of the lighter-weight "parent".

       Allows you to both load one or more modules, while setting up inheritance from those modules at the same time.  Roughly
       similar in effect to

           package Baz;
           BEGIN {
               require Foo;
               require Bar;
               push @ISA, qw(Foo Bar);
           }

       "base" employs some heuristics to determine if a module has already been loaded, if it has it doesn't try again. If
       "base" tries to "require" the module it will not die if it cannot find the module's file, but will die on any other
       error. After all this, should your base class be empty, containing no symbols, it will die. This is useful for inheriting
       from classes in the same file as yourself, like so:

               package Foo;
               sub exclaim { "I can have such a thing?!" }

               package Bar;
               use base "Foo";

       If $VERSION is not detected even after loading it, <base> will define $VERSION in the base package, setting it to the
       string "-1, set by base.pm".

       "base" will also initialize the fields if one of the base classes has it.  Multiple inheritance of fields is NOT
       supported, if two or more base classes each have inheritable fields the 'base' pragma will croak. See fields, public and
       protected for a description of this feature.

       The base class' "import" method is not called.

DIAGNOSTICS
       Base class package "%s" is empty.
           base.pm was unable to require the base package, because it was not found in your path.

       Class 'Foo' tried to inherit from itself
           Attempting to inherit from yourself generates a warning.

               use Foo;
               use base 'Foo';

HISTORY
       This module was introduced with Perl 5.004_04.

CAVEATS
       Due to the limitations of the implementation, you must use base before you declare any of your own fields.

SEE ALSO
       fields



perl v5.12.4                                               2011-06-07                                                  base(3pm)