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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);
           }

       When "base" tries to "require" a 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, "base"
       will die. This is useful for inheriting from classes in the same file
       as yourself but where the filename does not match the base module name,
       like so:

               # in Bar.pm
               package Foo;
               sub exclaim { "I can have such a thing?!" }

               package Bar;
               use base "Foo";

       There is no Foo.pm, but because "Foo" defines a symbol (the "exclaim"
       subroutine), "base" will not die when the "require" fails to load
       Foo.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 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.

               package 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(3)



perl v5.24.0                      2016-03-01                         base(3pm)

perl 5.24 - Generated Thu Nov 3 16:06:23 CDT 2016
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