base - Establish IS-A relationship with base class at compile time
Roughly similar in effect to
Will also initialize the %FIELDS hash if one of the base classes has
it. Multiple inheritance of %FIELDS is not supported. The 'base'
pragma will croak if multiple base classes have a %FIELDS hash. See
L<fields> for a description of this feature.
When strict 'vars' is in scope I<base> also let you assign to @ISA
without having to declare @ISA with the 'vars' pragma first.
If any of the base classes are not loaded yet, I<base> silently
C<require>s them. Whether to C<require> a base class package is
determined by the absence of a global $VERSION in the base package.
If $VERSION is not detected even after loading it, <base> will
define $VERSION in the base package, setting it to the string
This module was introduced with Perl 5.004_04.
next if $pkg->isa($base);
if ($vglob = ${"$base\::"}{VERSION
} and *$vglob{SCALAR
}) {
$$vglob = "-1, set by base.pm" unless defined $$vglob;
# Only ignore "Can't locate" errors from our eval require.
# Other fatal errors (syntax etc) must be reported.
die if $@
&& $@
!~ /^Can't locate .*? at \(eval /;
Carp
::croak
("Base class package \"$base\" is empty.\n",
"\t(Perhaps you need to 'use' the module ",
"which defines that package first.)");
${"$base\::VERSION"} = "-1, set by base.pm" unless defined ${"$base\::VERSION"};
push @
{"$pkg\::ISA"}, $base;
# A simple test like (defined %{"$base\::FIELDS"}) will
# sometimes produce typo warnings because it would create
# the hash if it was not present before.
if ($fglob = ${"$base\::"}{"FIELDS"} and *$fglob{HASH
}) {
Carp
::croak
("Can't multiply inherit %FIELDS");
fields
::inherit
($pkg, $fields_base);