phpman > man > base(3perl)

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