


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


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




perl v5.10.1                2009-10-12                          1





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


       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 v5.10.1                2009-10-12                          2


