Commit | Line | Data |
---|---|---|
dc6d0c4f JH |
1 | package base; |
2 | ||
864f8ab4 | 3 | use strict 'vars'; |
dc6d0c4f | 4 | use vars qw($VERSION); |
6df974e5 | 5 | $VERSION = '2.13'; |
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}; | |
28994922 | 21 | return( ($fglob && 'GLOB' eq ref($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 ($] < 5.009) { |
42 | *get_fields = sub { | |
9e998a43 RGS |
43 | # Shut up a possible typo warning. |
44 | () = \%{$_[0].'::FIELDS'}; | |
45 | my $f = \%{$_[0].'::FIELDS'}; | |
dc6d0c4f | 46 | |
9e998a43 RGS |
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'); | |
8731c5d9 | 51 | |
9e998a43 | 52 | return $f; |
8731c5d9 YK |
53 | } |
54 | } | |
55 | else { | |
56 | *get_fields = sub { | |
9e998a43 RGS |
57 | # Shut up a possible typo warning. |
58 | () = \%{$_[0].'::FIELDS'}; | |
59 | return \%{$_[0].'::FIELDS'}; | |
8731c5d9 | 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); | |
6df974e5 | 72 | my @isa_classes; |
dc6d0c4f | 73 | |
00ed247a | 74 | my @bases; |
dc6d0c4f | 75 | foreach my $base (@_) { |
9b6f3a27 CP |
76 | if ( $inheritor eq $base ) { |
77 | warn "Class '$inheritor' tried to inherit from itself\n"; | |
78 | } | |
79 | ||
00ed247a | 80 | next if grep $_->isa($base), ($inheritor, @bases); |
dc6d0c4f JH |
81 | |
82 | if (has_version($base)) { | |
9e998a43 RGS |
83 | ${$base.'::VERSION'} = '-1, set by base.pm' |
84 | unless defined ${$base.'::VERSION'}; | |
dc6d0c4f JH |
85 | } |
86 | else { | |
9e998a43 RGS |
87 | my $sigdie; |
88 | { | |
89 | local $SIG{__DIE__}; | |
90 | eval "require $base"; | |
91 | # Only ignore "Can't locate" errors from our eval require. | |
92 | # Other fatal errors (syntax etc) must be reported. | |
93 | die if $@ && $@ !~ /^Can't locate .*? at \(eval /; | |
94 | unless (%{"$base\::"}) { | |
95 | require Carp; | |
5565990a | 96 | local $" = " "; |
9e998a43 | 97 | Carp::croak(<<ERROR); |
dc6d0c4f | 98 | Base class package "$base" is empty. |
5565990a RGS |
99 | (Perhaps you need to 'use' the module which defines that package first, |
100 | or make that module available in \@INC (\@INC contains: @INC). | |
dc6d0c4f | 101 | ERROR |
9e998a43 | 102 | } |
bd3d0583 | 103 | $sigdie = $SIG{__DIE__} || undef; |
9e998a43 RGS |
104 | } |
105 | # Make sure a global $SIG{__DIE__} makes it out of the localization. | |
106 | $SIG{__DIE__} = $sigdie if defined $sigdie; | |
dc6d0c4f JH |
107 | ${$base.'::VERSION'} = "-1, set by base.pm" |
108 | unless defined ${$base.'::VERSION'}; | |
109 | } | |
00ed247a | 110 | push @bases, $base; |
dc6d0c4f | 111 | |
dc6d0c4f | 112 | if ( has_fields($base) || has_attr($base) ) { |
9e998a43 RGS |
113 | # No multiple fields inheritance *suck* |
114 | if ($fields_base) { | |
115 | require Carp; | |
116 | Carp::croak("Can't multiply inherit fields"); | |
117 | } else { | |
118 | $fields_base = $base; | |
119 | } | |
dc6d0c4f JH |
120 | } |
121 | } | |
6df974e5 RD |
122 | # Save this until the end so it's all or nothing if the above loop croaks. |
123 | push @{"$inheritor\::ISA"}, @isa_classes; | |
dc6d0c4f | 124 | |
00ed247a MS |
125 | push @{"$inheritor\::ISA"}, @bases; |
126 | ||
dc6d0c4f JH |
127 | if( defined $fields_base ) { |
128 | inherit_fields($inheritor, $fields_base); | |
129 | } | |
130 | } | |
131 | ||
132 | ||
133 | sub inherit_fields { | |
134 | my($derived, $base) = @_; | |
135 | ||
136 | return SUCCESS unless $base; | |
137 | ||
138 | my $battr = get_attr($base); | |
139 | my $dattr = get_attr($derived); | |
140 | my $dfields = get_fields($derived); | |
141 | my $bfields = get_fields($base); | |
142 | ||
143 | $dattr->[0] = @$battr; | |
144 | ||
145 | if( keys %$dfields ) { | |
9e998a43 RGS |
146 | warn <<"END"; |
147 | $derived is inheriting from $base but already has its own fields! | |
148 | This will cause problems. Be sure you use base BEFORE declaring fields. | |
149 | END | |
150 | ||
dc6d0c4f JH |
151 | } |
152 | ||
153 | # Iterate through the base's fields adding all the non-private | |
154 | # ones to the derived class. Hang on to the original attribute | |
155 | # (Public, Private, etc...) and add Inherited. | |
156 | # This is all too complicated to do efficiently with add_fields(). | |
157 | while (my($k,$v) = each %$bfields) { | |
158 | my $fno; | |
9e998a43 RGS |
159 | if ($fno = $dfields->{$k} and $fno != $v) { |
160 | require Carp; | |
161 | Carp::croak ("Inherited fields can't override existing fields"); | |
162 | } | |
dc6d0c4f JH |
163 | |
164 | if( $battr->[$v] & PRIVATE ) { | |
864f8ab4 | 165 | $dattr->[$v] = PRIVATE | INHERITED; |
dc6d0c4f JH |
166 | } |
167 | else { | |
168 | $dattr->[$v] = INHERITED | $battr->[$v]; | |
dc6d0c4f JH |
169 | $dfields->{$k} = $v; |
170 | } | |
171 | } | |
864f8ab4 | 172 | |
446e776f | 173 | foreach my $idx (1..$#{$battr}) { |
9e998a43 RGS |
174 | next if defined $dattr->[$idx]; |
175 | $dattr->[$idx] = $battr->[$idx] & INHERITED; | |
864f8ab4 | 176 | } |
dc6d0c4f JH |
177 | } |
178 | ||
179 | ||
180 | 1; | |
181 | ||
182 | __END__ | |
183 | ||
fb73857a | 184 | =head1 NAME |
185 | ||
9e998a43 | 186 | base - Establish an ISA relationship with base classes at compile time |
fb73857a | 187 | |
188 | =head1 SYNOPSIS | |
189 | ||
190 | package Baz; | |
fb73857a | 191 | use base qw(Foo Bar); |
192 | ||
193 | =head1 DESCRIPTION | |
194 | ||
45e8908f EM |
195 | Allows you to both load one or more modules, while setting up inheritance from |
196 | those modules at the same time. Roughly similar in effect to | |
fb73857a | 197 | |
45e8908f | 198 | package Baz; |
fb73857a | 199 | BEGIN { |
dc6d0c4f JH |
200 | require Foo; |
201 | require Bar; | |
202 | push @ISA, qw(Foo Bar); | |
fb73857a | 203 | } |
204 | ||
9e998a43 RGS |
205 | C<base> employs some heuristics to determine if a module has already been |
206 | loaded, if it has it doesn't try again. If C<base> tries to C<require> the | |
207 | module it will not die if it cannot find the module's file, but will die on any | |
208 | other error. After all this, should your base class be empty, containing no | |
209 | symbols, it will die. This is useful for inheriting from classes in the same | |
210 | file as yourself, like so: | |
211 | ||
212 | package Foo; | |
213 | sub exclaim { "I can have such a thing?!" } | |
214 | ||
215 | package Bar; | |
216 | use base "Foo"; | |
217 | ||
218 | If $VERSION is not detected even after loading it, <base> will define $VERSION | |
219 | in the base package, setting it to the string C<-1, set by base.pm>. | |
220 | ||
221 | C<base> will also initialize the fields if one of the base classes has it. | |
222 | Multiple inheritance of fields is B<NOT> supported, if two or more base classes | |
223 | each have inheritable fields the 'base' pragma will croak. See L<fields>, | |
224 | L<public> and L<protected> for a description of this feature. | |
225 | ||
226 | The base class' C<import> method is B<not> called. | |
45e8908f | 227 | |
f1192cee | 228 | |
36c726b3 JB |
229 | =head1 DIAGNOSTICS |
230 | ||
231 | =over 4 | |
232 | ||
233 | =item Base class package "%s" is empty. | |
234 | ||
235 | base.pm was unable to require the base package, because it was not | |
236 | found in your path. | |
237 | ||
9e998a43 | 238 | =item Class 'Foo' tried to inherit from itself |
36c726b3 | 239 | |
9e998a43 | 240 | Attempting to inherit from yourself generates a warning. |
b8bc843f | 241 | |
9e998a43 RGS |
242 | use Foo; |
243 | use base 'Foo'; | |
fb73857a | 244 | |
9e998a43 | 245 | =back |
9b6f3a27 | 246 | |
9e998a43 | 247 | =head1 HISTORY |
9b6f3a27 | 248 | |
9e998a43 | 249 | This module was introduced with Perl 5.004_04. |
fb73857a | 250 | |
dc6d0c4f | 251 | =head1 CAVEATS |
fb73857a | 252 | |
45e8908f | 253 | Due to the limitations of the implementation, you must use |
dc6d0c4f | 254 | base I<before> you declare any of your own fields. |
17f410f9 | 255 | |
fb73857a | 256 | |
dc6d0c4f | 257 | =head1 SEE ALSO |
fb73857a | 258 | |
dc6d0c4f | 259 | L<fields> |
fb73857a | 260 | |
dc6d0c4f | 261 | =cut |