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