Commit | Line | Data |
---|---|---|
dc6d0c4f JH |
1 | package base; |
2 | ||
864f8ab4 | 3 | use strict 'vars'; |
dc6d0c4f | 4 | use vars qw($VERSION); |
9b6f3a27 | 5 | $VERSION = '2.08'; |
dc6d0c4f JH |
6 | |
7 | # constant.pm is slow | |
8 | sub SUCCESS () { 1 } | |
9 | ||
10 | sub PUBLIC () { 2**0 } | |
11 | sub PRIVATE () { 2**1 } | |
12 | sub INHERITED () { 2**2 } | |
13 | sub PROTECTED () { 2**3 } | |
14 | ||
15 | ||
16 | my $Fattr = \%fields::attr; | |
17 | ||
18 | sub has_fields { | |
19 | my($base) = shift; | |
20 | my $fglob = ${"$base\::"}{FIELDS}; | |
864f8ab4 | 21 | return( ($fglob && *$fglob{HASH}) ? 1 : 0 ); |
dc6d0c4f JH |
22 | } |
23 | ||
24 | sub has_version { | |
25 | my($base) = shift; | |
26 | my $vglob = ${$base.'::'}{VERSION}; | |
864f8ab4 | 27 | return( ($vglob && *$vglob{SCALAR}) ? 1 : 0 ); |
dc6d0c4f JH |
28 | } |
29 | ||
30 | sub has_attr { | |
31 | my($proto) = shift; | |
32 | my($class) = ref $proto || $proto; | |
33 | return exists $Fattr->{$class}; | |
34 | } | |
35 | ||
36 | sub get_attr { | |
37 | $Fattr->{$_[0]} = [1] unless $Fattr->{$_[0]}; | |
38 | return $Fattr->{$_[0]}; | |
39 | } | |
40 | ||
8731c5d9 YK |
41 | if ($] < 5.009) { |
42 | *get_fields = sub { | |
43 | # Shut up a possible typo warning. | |
44 | () = \%{$_[0].'::FIELDS'}; | |
45 | my $f = \%{$_[0].'::FIELDS'}; | |
dc6d0c4f | 46 | |
8731c5d9 YK |
47 | # should be centralized in fields? perhaps |
48 | # fields::mk_FIELDS_be_OK. Peh. As long as %{ $package . '::FIELDS' } | |
49 | # is used here anyway, it doesn't matter. | |
50 | bless $f, 'pseudohash' if (ref($f) ne 'pseudohash'); | |
51 | ||
52 | return $f; | |
53 | } | |
54 | } | |
55 | else { | |
56 | *get_fields = sub { | |
57 | # Shut up a possible typo warning. | |
58 | () = \%{$_[0].'::FIELDS'}; | |
59 | return \%{$_[0].'::FIELDS'}; | |
60 | } | |
dc6d0c4f JH |
61 | } |
62 | ||
dc6d0c4f JH |
63 | sub import { |
64 | my $class = shift; | |
65 | ||
66 | return SUCCESS unless @_; | |
67 | ||
68 | # List of base classes from which we will inherit %FIELDS. | |
69 | my $fields_base; | |
70 | ||
71 | my $inheritor = caller(0); | |
72 | ||
73 | foreach my $base (@_) { | |
9b6f3a27 CP |
74 | if ( $inheritor eq $base ) { |
75 | warn "Class '$inheritor' tried to inherit from itself\n"; | |
76 | } | |
77 | ||
dc6d0c4f JH |
78 | next if $inheritor->isa($base); |
79 | ||
80 | if (has_version($base)) { | |
81 | ${$base.'::VERSION'} = '-1, set by base.pm' | |
82 | unless defined ${$base.'::VERSION'}; | |
83 | } | |
84 | else { | |
a7fce7e1 | 85 | local $SIG{__DIE__}; |
dc6d0c4f JH |
86 | eval "require $base"; |
87 | # Only ignore "Can't locate" errors from our eval require. | |
88 | # Other fatal errors (syntax etc) must be reported. | |
89 | die if $@ && $@ !~ /^Can't locate .*? at \(eval /; | |
90 | unless (%{"$base\::"}) { | |
91 | require Carp; | |
92 | Carp::croak(<<ERROR); | |
93 | Base class package "$base" is empty. | |
94 | (Perhaps you need to 'use' the module which defines that package first.) | |
95 | ERROR | |
96 | ||
97 | } | |
98 | ${$base.'::VERSION'} = "-1, set by base.pm" | |
99 | unless defined ${$base.'::VERSION'}; | |
100 | } | |
101 | push @{"$inheritor\::ISA"}, $base; | |
102 | ||
dc6d0c4f | 103 | if ( has_fields($base) || has_attr($base) ) { |
3c4b39be | 104 | # No multiple fields inheritance *suck* |
864f8ab4 JH |
105 | if ($fields_base) { |
106 | require Carp; | |
107 | Carp::croak("Can't multiply inherit %FIELDS"); | |
108 | } else { | |
109 | $fields_base = $base; | |
dc6d0c4f JH |
110 | } |
111 | } | |
112 | } | |
113 | ||
114 | if( defined $fields_base ) { | |
115 | inherit_fields($inheritor, $fields_base); | |
116 | } | |
117 | } | |
118 | ||
119 | ||
120 | sub inherit_fields { | |
121 | my($derived, $base) = @_; | |
122 | ||
123 | return SUCCESS unless $base; | |
124 | ||
125 | my $battr = get_attr($base); | |
126 | my $dattr = get_attr($derived); | |
127 | my $dfields = get_fields($derived); | |
128 | my $bfields = get_fields($base); | |
129 | ||
130 | $dattr->[0] = @$battr; | |
131 | ||
132 | if( keys %$dfields ) { | |
133 | warn "$derived is inheriting from $base but already has its own ". | |
134 | "fields!\n". | |
45e8908f | 135 | "This will cause problems.\n". |
dc6d0c4f JH |
136 | "Be sure you use base BEFORE declaring fields\n"; |
137 | } | |
138 | ||
139 | # Iterate through the base's fields adding all the non-private | |
140 | # ones to the derived class. Hang on to the original attribute | |
141 | # (Public, Private, etc...) and add Inherited. | |
142 | # This is all too complicated to do efficiently with add_fields(). | |
143 | while (my($k,$v) = each %$bfields) { | |
144 | my $fno; | |
145 | if ($fno = $dfields->{$k} and $fno != $v) { | |
146 | require Carp; | |
147 | Carp::croak ("Inherited %FIELDS can't override existing %FIELDS"); | |
148 | } | |
149 | ||
150 | if( $battr->[$v] & PRIVATE ) { | |
864f8ab4 | 151 | $dattr->[$v] = PRIVATE | INHERITED; |
dc6d0c4f JH |
152 | } |
153 | else { | |
154 | $dattr->[$v] = INHERITED | $battr->[$v]; | |
dc6d0c4f JH |
155 | $dfields->{$k} = $v; |
156 | } | |
157 | } | |
864f8ab4 | 158 | |
446e776f DM |
159 | foreach my $idx (1..$#{$battr}) { |
160 | next if defined $dattr->[$idx]; | |
161 | $dattr->[$idx] = $battr->[$idx] & INHERITED; | |
864f8ab4 | 162 | } |
dc6d0c4f JH |
163 | } |
164 | ||
165 | ||
166 | 1; | |
167 | ||
168 | __END__ | |
169 | ||
fb73857a | 170 | =head1 NAME |
171 | ||
45e8908f | 172 | base - Establish IS-A relationship with base classes at compile time |
fb73857a | 173 | |
174 | =head1 SYNOPSIS | |
175 | ||
176 | package Baz; | |
fb73857a | 177 | use base qw(Foo Bar); |
178 | ||
179 | =head1 DESCRIPTION | |
180 | ||
45e8908f EM |
181 | Allows you to both load one or more modules, while setting up inheritance from |
182 | those modules at the same time. Roughly similar in effect to | |
fb73857a | 183 | |
45e8908f | 184 | package Baz; |
fb73857a | 185 | BEGIN { |
dc6d0c4f JH |
186 | require Foo; |
187 | require Bar; | |
188 | push @ISA, qw(Foo Bar); | |
fb73857a | 189 | } |
190 | ||
45e8908f EM |
191 | If any of the listed modules are not loaded yet, I<base> silently attempts to |
192 | C<require> them (and silently continues if the C<require> failed). Whether to | |
193 | C<require> a base class module is determined by the absence of a global variable | |
194 | $VERSION in the base package. If $VERSION is not detected even after loading | |
195 | it, <base> will define $VERSION in the base package, setting it to the string | |
196 | C<-1, set by base.pm>. | |
197 | ||
dc6d0c4f | 198 | Will also initialize the fields if one of the base classes has it. |
3c4b39be | 199 | Multiple inheritance of fields is B<NOT> supported, if two or more |
dc6d0c4f JH |
200 | base classes each have inheritable fields the 'base' pragma will |
201 | croak. See L<fields>, L<public> and L<protected> for a description of | |
202 | this feature. | |
f1192cee | 203 | |
36c726b3 JB |
204 | =head1 DIAGNOSTICS |
205 | ||
206 | =over 4 | |
207 | ||
208 | =item Base class package "%s" is empty. | |
209 | ||
210 | base.pm was unable to require the base package, because it was not | |
211 | found in your path. | |
212 | ||
213 | =back | |
214 | ||
b8bc843f A |
215 | =head1 HISTORY |
216 | ||
fb73857a | 217 | This module was introduced with Perl 5.004_04. |
218 | ||
9b6f3a27 CP |
219 | Attempting to inherit from yourself generates a warning: |
220 | ||
221 | use Foo; | |
222 | use base 'Foo'; | |
223 | ||
224 | # Class 'Foo' tried to inherit from itself | |
fb73857a | 225 | |
dc6d0c4f | 226 | =head1 CAVEATS |
fb73857a | 227 | |
45e8908f | 228 | Due to the limitations of the implementation, you must use |
dc6d0c4f | 229 | base I<before> you declare any of your own fields. |
17f410f9 | 230 | |
fb73857a | 231 | |
dc6d0c4f | 232 | =head1 SEE ALSO |
fb73857a | 233 | |
dc6d0c4f | 234 | L<fields> |
fb73857a | 235 | |
dc6d0c4f | 236 | =cut |