Commit | Line | Data |
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fb73857a | 1 | =head1 NAME |
2 | ||
3 | base - Establish IS-A relationship with base class at compile time | |
4 | ||
5 | =head1 SYNOPSIS | |
6 | ||
7 | package Baz; | |
fb73857a | 8 | use base qw(Foo Bar); |
9 | ||
10 | =head1 DESCRIPTION | |
11 | ||
12 | Roughly similar in effect to | |
13 | ||
14 | BEGIN { | |
15 | require Foo; | |
16 | require Bar; | |
17 | push @ISA, qw(Foo Bar); | |
18 | } | |
19 | ||
f1192cee GA |
20 | Will also initialize the %FIELDS hash if one of the base classes has |
21 | it. Multiple inheritance of %FIELDS is not supported. The 'base' | |
22 | pragma will croak if multiple base classes has a %FIELDS hash. See | |
23 | L<fields> for a description of this feature. | |
24 | ||
25 | When strict 'vars' is in scope I<base> also let you assign to @ISA | |
26 | without having to declare @ISA with the 'vars' pragma first. | |
27 | ||
fb73857a | 28 | This module was introduced with Perl 5.004_04. |
29 | ||
f1192cee | 30 | =head1 SEE ALSO |
fb73857a | 31 | |
f1192cee | 32 | L<fields> |
fb73857a | 33 | |
34 | =cut | |
35 | ||
36 | package base; | |
37 | ||
38 | sub import { | |
39 | my $class = shift; | |
f1192cee | 40 | my $fields_base; |
fb73857a | 41 | |
42 | foreach my $base (@_) { | |
43 | unless (defined %{"$base\::"}) { | |
44 | eval "require $base"; | |
9b599b2a GS |
45 | # Only ignore "Can't locate" errors from our eval require. |
46 | # Other fatal errors (syntax etc) must be reported. | |
47 | die if $@ && $@ !~ /^Can't locate .*? at \(eval /; | |
fb73857a | 48 | unless (defined %{"$base\::"}) { |
49 | require Carp; | |
50 | Carp::croak("Base class package \"$base\" is empty.\n", | |
51 | "\t(Perhaps you need to 'use' the module ", | |
52 | "which defines that package first.)"); | |
53 | } | |
54 | } | |
f1192cee GA |
55 | |
56 | # A simple test like (defined %{"$base\::FIELDS"}) will | |
57 | # sometimes produce typo warnings because it would create | |
58 | # the hash if it was not present before. | |
59 | my $fglob; | |
60 | if ($fglob = ${"$base\::"}{"FIELDS"} and *$fglob{HASH}) { | |
61 | if ($fields_base) { | |
62 | require Carp; | |
63 | Carp::croak("Can't multiply inherit %FIELDS"); | |
64 | } else { | |
65 | $fields_base = $base; | |
66 | } | |
67 | } | |
68 | } | |
69 | my $pkg = caller(0); | |
70 | push @{"$pkg\::ISA"}, @_; | |
71 | if ($fields_base) { | |
72 | require fields; | |
73 | fields::inherit($pkg, $fields_base); | |
fb73857a | 74 | } |
fb73857a | 75 | } |
76 | ||
77 | 1; |