=head1 NAME base - Establish IS-A relationship with base class at compile time =head1 SYNOPSIS package Baz; use base qw(Foo Bar); =head1 DESCRIPTION Roughly similar in effect to BEGIN { require Foo; require Bar; push @ISA, qw(Foo Bar); } 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 for a description of this feature. When strict 'vars' is in scope I 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 silently Cs them. Whether to C 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, will define $VERSION in the base package, setting it to the string C<-1, defined by base.pm>. =head1 HISTORY This module was introduced with Perl 5.004_04. =head1 SEE ALSO L =cut package base; use 5.005_64; our $VERSION = "1.01"; sub import { my $class = shift; my $fields_base; my $pkg = caller(0); foreach my $base (@_) { next if $pkg->isa($base); push @{"$pkg\::ISA"}, $base; unless (exists ${"$base\::"}{VERSION}) { eval "require $base"; # 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 /; unless (%{"$base\::"}) { require Carp; Carp::croak("Base class package \"$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 exists ${"$base\::"}{VERSION}; } # A simple test like (defined %{"$base\::FIELDS"}) will # sometimes produce typo warnings because it would create # the hash if it was not present before. my $fglob; if ($fglob = ${"$base\::"}{"FIELDS"} and *$fglob{HASH}) { if ($fields_base) { require Carp; Carp::croak("Can't multiply inherit %FIELDS"); } else { $fields_base = $base; } } } if ($fields_base) { require fields; fields::inherit($pkg, $fields_base); } } 1;