Commit | Line | Data |
---|---|---|
e4783b1c | 1 | package NEXT; |
3c2847f4 | 2 | $VERSION = '0.64'; |
e4783b1c JH |
3 | use Carp; |
4 | use strict; | |
5dd54fb4 | 5 | use overload (); |
e4783b1c | 6 | |
52138ef3 | 7 | sub NEXT::ELSEWHERE::ancestors |
e4783b1c | 8 | { |
13021a80 | 9 | my @inlist = shift; |
e4783b1c | 10 | my @outlist = (); |
13021a80 JH |
11 | while (my $next = shift @inlist) { |
12 | push @outlist, $next; | |
e4783b1c JH |
13 | no strict 'refs'; |
14 | unshift @inlist, @{"$outlist[-1]::ISA"}; | |
15 | } | |
16 | return @outlist; | |
17 | } | |
18 | ||
bf5734d4 JH |
19 | sub NEXT::ELSEWHERE::ordered_ancestors |
20 | { | |
21 | my @inlist = shift; | |
22 | my @outlist = (); | |
23 | while (my $next = shift @inlist) { | |
24 | push @outlist, $next; | |
25 | no strict 'refs'; | |
26 | push @inlist, @{"$outlist[-1]::ISA"}; | |
27 | } | |
28 | return sort { $a->isa($b) ? -1 | |
29 | : $b->isa($a) ? +1 | |
30 | : 0 } @outlist; | |
31 | } | |
32 | ||
597fc7a0 | 33 | sub NEXT::ELSEWHERE::buildAUTOLOAD |
e4783b1c | 34 | { |
597fc7a0 RGS |
35 | my $autoload_name = caller() . '::AUTOLOAD'; |
36 | ||
37 | no strict 'refs'; | |
38 | *{$autoload_name} = sub { | |
39 | my ($self) = @_; | |
40 | my $depth = 1; | |
41 | until (((caller($depth))[3]||q{}) !~ /^\(eval\)$/) { $depth++ } | |
42 | my $caller = (caller($depth))[3]; | |
43 | my $wanted = $NEXT::AUTOLOAD || $autoload_name; | |
44 | undef $NEXT::AUTOLOAD; | |
3c2847f4 FR |
45 | my ($caller_class, $caller_method) = do { $caller =~ m{(.*)::(.*)}g }; |
46 | my ($wanted_class, $wanted_method) = do { $wanted =~ m{(.*)::(.*)}g }; | |
597fc7a0 RGS |
47 | croak "Can't call $wanted from $caller" |
48 | unless $caller_method eq $wanted_method; | |
49 | ||
50 | my $key = ref $self && overload::Overloaded($self) | |
51 | ? overload::StrVal($self) : $self; | |
52 | ||
53 | local ($NEXT::NEXT{$key,$wanted_method}, $NEXT::SEEN) = | |
54 | ($NEXT::NEXT{$key,$wanted_method}, $NEXT::SEEN); | |
55 | ||
56 | unless ($NEXT::NEXT{$key,$wanted_method}) { | |
57 | my @forebears = | |
58 | NEXT::ELSEWHERE::ancestors ref $self || $self, | |
59 | $wanted_class; | |
60 | while (@forebears) { | |
61 | last if shift @forebears eq $caller_class | |
62 | } | |
63 | no strict 'refs'; | |
082b74eb FR |
64 | @{$NEXT::NEXT{$key,$wanted_method}} = |
65 | map { | |
66 | my $stash = \%{"${_}::"}; | |
67 | ($stash->{$caller_method} && (*{$stash->{$caller_method}}{CODE})) | |
68 | ? *{$stash->{$caller_method}}{CODE} | |
69 | : () } @forebears | |
597fc7a0 | 70 | unless $wanted_method eq 'AUTOLOAD'; |
082b74eb FR |
71 | @{$NEXT::NEXT{$key,$wanted_method}} = |
72 | map { | |
73 | my $stash = \%{"${_}::"}; | |
74 | ($stash->{AUTOLOAD} && (*{$stash->{AUTOLOAD}}{CODE})) | |
75 | ? "${_}::AUTOLOAD" | |
76 | : () } @forebears | |
597fc7a0 RGS |
77 | unless @{$NEXT::NEXT{$key,$wanted_method}||[]}; |
78 | $NEXT::SEEN->{$key,*{$caller}{CODE}}++; | |
79 | } | |
80 | my $call_method = shift @{$NEXT::NEXT{$key,$wanted_method}}; | |
3c2847f4 | 81 | while (do { $wanted_class =~ /^NEXT\b.*\b(UNSEEN|DISTINCT)\b/ } |
597fc7a0 RGS |
82 | && defined $call_method |
83 | && $NEXT::SEEN->{$key,$call_method}++) { | |
84 | $call_method = shift @{$NEXT::NEXT{$key,$wanted_method}}; | |
85 | } | |
86 | unless (defined $call_method) { | |
3c2847f4 | 87 | return unless do { $wanted_class =~ /^NEXT:.*:ACTUAL/ }; |
597fc7a0 RGS |
88 | (local $Carp::CarpLevel)++; |
89 | croak qq(Can't locate object method "$wanted_method" ), | |
90 | qq(via package "$caller_class"); | |
91 | }; | |
92 | return $self->$call_method(@_[1..$#_]) if ref $call_method eq 'CODE'; | |
93 | no strict 'refs'; | |
3c2847f4 | 94 | do { ($wanted_method=${$caller_class."::AUTOLOAD"}) =~ s/.*::// } |
597fc7a0 RGS |
95 | if $wanted_method eq 'AUTOLOAD'; |
96 | $$call_method = $caller_class."::NEXT::".$wanted_method; | |
97 | return $call_method->(@_); | |
98 | }; | |
e4783b1c JH |
99 | } |
100 | ||
13021a80 | 101 | no strict 'vars'; |
597fc7a0 RGS |
102 | package NEXT; NEXT::ELSEWHERE::buildAUTOLOAD(); |
103 | package NEXT::UNSEEN; @ISA = 'NEXT'; NEXT::ELSEWHERE::buildAUTOLOAD(); | |
104 | package NEXT::DISTINCT; @ISA = 'NEXT'; NEXT::ELSEWHERE::buildAUTOLOAD(); | |
105 | package NEXT::ACTUAL; @ISA = 'NEXT'; NEXT::ELSEWHERE::buildAUTOLOAD(); | |
106 | package NEXT::ACTUAL::UNSEEN; @ISA = 'NEXT'; NEXT::ELSEWHERE::buildAUTOLOAD(); | |
107 | package NEXT::ACTUAL::DISTINCT; @ISA = 'NEXT'; NEXT::ELSEWHERE::buildAUTOLOAD(); | |
108 | package NEXT::UNSEEN::ACTUAL; @ISA = 'NEXT'; NEXT::ELSEWHERE::buildAUTOLOAD(); | |
109 | package NEXT::DISTINCT::ACTUAL; @ISA = 'NEXT'; NEXT::ELSEWHERE::buildAUTOLOAD(); | |
110 | ||
111 | package EVERY; | |
112 | ||
113 | sub EVERY::ELSEWHERE::buildAUTOLOAD { | |
114 | my $autoload_name = caller() . '::AUTOLOAD'; | |
115 | ||
116 | no strict 'refs'; | |
117 | *{$autoload_name} = sub { | |
118 | my ($self) = @_; | |
119 | my $depth = 1; | |
120 | until (((caller($depth))[3]||q{}) !~ /^\(eval\)$/) { $depth++ } | |
121 | my $caller = (caller($depth))[3]; | |
122 | my $wanted = $EVERY::AUTOLOAD || $autoload_name; | |
123 | undef $EVERY::AUTOLOAD; | |
3c2847f4 | 124 | my ($wanted_class, $wanted_method) = do { $wanted =~ m{(.*)::(.*)}g }; |
597fc7a0 RGS |
125 | |
126 | my $key = ref($self) && overload::Overloaded($self) | |
127 | ? overload::StrVal($self) : $self; | |
128 | ||
129 | local $NEXT::ALREADY_IN_EVERY{$key,$wanted_method} = | |
130 | $NEXT::ALREADY_IN_EVERY{$key,$wanted_method}; | |
131 | ||
132 | return if $NEXT::ALREADY_IN_EVERY{$key,$wanted_method}++; | |
133 | ||
134 | my @forebears = NEXT::ELSEWHERE::ordered_ancestors ref $self || $self, | |
135 | $wanted_class; | |
3c2847f4 | 136 | @forebears = reverse @forebears if do { $wanted_class =~ /\bLAST\b/ }; |
597fc7a0 RGS |
137 | no strict 'refs'; |
138 | my %seen; | |
139 | my @every = map { my $sub = "${_}::$wanted_method"; | |
140 | !*{$sub}{CODE} || $seen{$sub}++ ? () : $sub | |
141 | } @forebears | |
142 | unless $wanted_method eq 'AUTOLOAD'; | |
143 | ||
144 | my $want = wantarray; | |
145 | if (@every) { | |
146 | if ($want) { | |
147 | return map {($_, [$self->$_(@_[1..$#_])])} @every; | |
148 | } | |
149 | elsif (defined $want) { | |
150 | return { map {($_, scalar($self->$_(@_[1..$#_])))} | |
151 | @every | |
152 | }; | |
153 | } | |
154 | else { | |
155 | $self->$_(@_[1..$#_]) for @every; | |
156 | return; | |
157 | } | |
158 | } | |
159 | ||
160 | @every = map { my $sub = "${_}::AUTOLOAD"; | |
161 | !*{$sub}{CODE} || $seen{$sub}++ ? () : "${_}::AUTOLOAD" | |
162 | } @forebears; | |
163 | if ($want) { | |
164 | return map { $$_ = ref($self)."::EVERY::".$wanted_method; | |
165 | ($_, [$self->$_(@_[1..$#_])]); | |
166 | } @every; | |
167 | } | |
168 | elsif (defined $want) { | |
169 | return { map { $$_ = ref($self)."::EVERY::".$wanted_method; | |
170 | ($_, scalar($self->$_(@_[1..$#_]))) | |
171 | } @every | |
172 | }; | |
173 | } | |
174 | else { | |
175 | for (@every) { | |
176 | $$_ = ref($self)."::EVERY::".$wanted_method; | |
177 | $self->$_(@_[1..$#_]); | |
178 | } | |
179 | return; | |
180 | } | |
181 | }; | |
bf5734d4 JH |
182 | } |
183 | ||
597fc7a0 RGS |
184 | package EVERY::LAST; @ISA = 'EVERY'; EVERY::ELSEWHERE::buildAUTOLOAD(); |
185 | package EVERY; @ISA = 'NEXT'; EVERY::ELSEWHERE::buildAUTOLOAD(); | |
13021a80 | 186 | |
e4783b1c JH |
187 | 1; |
188 | ||
189 | __END__ | |
190 | ||
191 | =head1 NAME | |
192 | ||
bf5734d4 | 193 | NEXT.pm - Provide a pseudo-class NEXT (et al) that allows method redispatch |
e4783b1c JH |
194 | |
195 | ||
196 | =head1 SYNOPSIS | |
197 | ||
13021a80 | 198 | use NEXT; |
e4783b1c | 199 | |
13021a80 JH |
200 | package A; |
201 | sub A::method { print "$_[0]: A method\n"; $_[0]->NEXT::method() } | |
202 | sub A::DESTROY { print "$_[0]: A dtor\n"; $_[0]->NEXT::DESTROY() } | |
e4783b1c | 203 | |
13021a80 JH |
204 | package B; |
205 | use base qw( A ); | |
206 | sub B::AUTOLOAD { print "$_[0]: B AUTOLOAD\n"; $_[0]->NEXT::AUTOLOAD() } | |
207 | sub B::DESTROY { print "$_[0]: B dtor\n"; $_[0]->NEXT::DESTROY() } | |
e4783b1c | 208 | |
13021a80 JH |
209 | package C; |
210 | sub C::method { print "$_[0]: C method\n"; $_[0]->NEXT::method() } | |
211 | sub C::AUTOLOAD { print "$_[0]: C AUTOLOAD\n"; $_[0]->NEXT::AUTOLOAD() } | |
212 | sub C::DESTROY { print "$_[0]: C dtor\n"; $_[0]->NEXT::DESTROY() } | |
e4783b1c | 213 | |
13021a80 JH |
214 | package D; |
215 | use base qw( B C ); | |
216 | sub D::method { print "$_[0]: D method\n"; $_[0]->NEXT::method() } | |
217 | sub D::AUTOLOAD { print "$_[0]: D AUTOLOAD\n"; $_[0]->NEXT::AUTOLOAD() } | |
218 | sub D::DESTROY { print "$_[0]: D dtor\n"; $_[0]->NEXT::DESTROY() } | |
e4783b1c | 219 | |
13021a80 | 220 | package main; |
e4783b1c | 221 | |
13021a80 | 222 | my $obj = bless {}, "D"; |
e4783b1c | 223 | |
13021a80 JH |
224 | $obj->method(); # Calls D::method, A::method, C::method |
225 | $obj->missing_method(); # Calls D::AUTOLOAD, B::AUTOLOAD, C::AUTOLOAD | |
e4783b1c | 226 | |
13021a80 | 227 | # Clean-up calls D::DESTROY, B::DESTROY, A::DESTROY, C::DESTROY |
e4783b1c JH |
228 | |
229 | ||
bf5734d4 | 230 | |
e4783b1c JH |
231 | =head1 DESCRIPTION |
232 | ||
233 | NEXT.pm adds a pseudoclass named C<NEXT> to any program | |
e23eab12 | 234 | that uses it. If a method C<m> calls C<$self-E<gt>NEXT::m()>, the call to |
e4783b1c JH |
235 | C<m> is redispatched as if the calling method had not originally been found. |
236 | ||
e23eab12 | 237 | In other words, a call to C<$self-E<gt>NEXT::m()> resumes the depth-first, |
55a1c97c JH |
238 | left-to-right search of C<$self>'s class hierarchy that resulted in the |
239 | original call to C<m>. | |
240 | ||
e23eab12 | 241 | Note that this is not the same thing as C<$self-E<gt>SUPER::m()>, which |
55a1c97c | 242 | begins a new dispatch that is restricted to searching the ancestors |
e23eab12 | 243 | of the current class. C<$self-E<gt>NEXT::m()> can backtrack |
55a1c97c | 244 | past the current class -- to look for a suitable method in other |
e23eab12 | 245 | ancestors of C<$self> -- whereas C<$self-E<gt>SUPER::m()> cannot. |
e4783b1c JH |
246 | |
247 | A typical use would be in the destructors of a class hierarchy, | |
248 | as illustrated in the synopsis above. Each class in the hierarchy | |
249 | has a DESTROY method that performs some class-specific action | |
250 | and then redispatches the call up the hierarchy. As a result, | |
251 | when an object of class D is destroyed, the destructors of I<all> | |
252 | its parent classes are called (in depth-first, left-to-right order). | |
253 | ||
254 | Another typical use of redispatch would be in C<AUTOLOAD>'ed methods. | |
255 | If such a method determined that it was not able to handle a | |
256 | particular call, it might choose to redispatch that call, in the | |
257 | hope that some other C<AUTOLOAD> (above it, or to its left) might | |
258 | do better. | |
259 | ||
13021a80 JH |
260 | By default, if a redispatch attempt fails to find another method |
261 | elsewhere in the objects class hierarchy, it quietly gives up and does | |
3c4b39be | 262 | nothing (but see L<"Enforcing redispatch">). This gracious acquiescence |
13021a80 JH |
263 | is also unlike the (generally annoying) behaviour of C<SUPER>, which |
264 | throws an exception if it cannot redispatch. | |
265 | ||
e4783b1c | 266 | Note that it is a fatal error for any method (including C<AUTOLOAD>) |
13021a80 JH |
267 | to attempt to redispatch any method that does not have the |
268 | same name. For example: | |
269 | ||
270 | sub D::oops { print "oops!\n"; $_[0]->NEXT::other_method() } | |
271 | ||
272 | ||
273 | =head2 Enforcing redispatch | |
274 | ||
275 | It is possible to make C<NEXT> redispatch more demandingly (i.e. like | |
276 | C<SUPER> does), so that the redispatch throws an exception if it cannot | |
277 | find a "next" method to call. | |
278 | ||
279 | To do this, simple invoke the redispatch as: | |
280 | ||
281 | $self->NEXT::ACTUAL::method(); | |
282 | ||
283 | rather than: | |
284 | ||
285 | $self->NEXT::method(); | |
286 | ||
287 | The C<ACTUAL> tells C<NEXT> that there must actually be a next method to call, | |
288 | or it should throw an exception. | |
289 | ||
290 | C<NEXT::ACTUAL> is most commonly used in C<AUTOLOAD> methods, as a means to | |
291 | decline an C<AUTOLOAD> request, but preserve the normal exception-on-failure | |
292 | semantics: | |
293 | ||
294 | sub AUTOLOAD { | |
295 | if ($AUTOLOAD =~ /foo|bar/) { | |
296 | # handle here | |
297 | } | |
298 | else { # try elsewhere | |
299 | shift()->NEXT::ACTUAL::AUTOLOAD(@_); | |
300 | } | |
301 | } | |
302 | ||
303 | By using C<NEXT::ACTUAL>, if there is no other C<AUTOLOAD> to handle the | |
304 | method call, an exception will be thrown (as usually happens in the absence of | |
305 | a suitable C<AUTOLOAD>). | |
306 | ||
307 | ||
308 | =head2 Avoiding repetitions | |
309 | ||
310 | If C<NEXT> redispatching is used in the methods of a "diamond" class hierarchy: | |
311 | ||
312 | # A B | |
313 | # / \ / | |
314 | # C D | |
315 | # \ / | |
316 | # E | |
317 | ||
318 | use NEXT; | |
319 | ||
320 | package A; | |
321 | sub foo { print "called A::foo\n"; shift->NEXT::foo() } | |
322 | ||
323 | package B; | |
324 | sub foo { print "called B::foo\n"; shift->NEXT::foo() } | |
325 | ||
326 | package C; @ISA = qw( A ); | |
327 | sub foo { print "called C::foo\n"; shift->NEXT::foo() } | |
328 | ||
329 | package D; @ISA = qw(A B); | |
330 | sub foo { print "called D::foo\n"; shift->NEXT::foo() } | |
331 | ||
332 | package E; @ISA = qw(C D); | |
333 | sub foo { print "called E::foo\n"; shift->NEXT::foo() } | |
334 | ||
335 | E->foo(); | |
336 | ||
337 | then derived classes may (re-)inherit base-class methods through two or | |
338 | more distinct paths (e.g. in the way C<E> inherits C<A::foo> twice -- | |
339 | through C<C> and C<D>). In such cases, a sequence of C<NEXT> redispatches | |
340 | will invoke the multiply inherited method as many times as it is | |
341 | inherited. For example, the above code prints: | |
342 | ||
343 | called E::foo | |
344 | called C::foo | |
345 | called A::foo | |
346 | called D::foo | |
347 | called A::foo | |
348 | called B::foo | |
349 | ||
350 | (i.e. C<A::foo> is called twice). | |
351 | ||
352 | In some cases this I<may> be the desired effect within a diamond hierarchy, | |
353 | but in others (e.g. for destructors) it may be more appropriate to | |
354 | call each method only once during a sequence of redispatches. | |
355 | ||
356 | To cover such cases, you can redispatch methods via: | |
357 | ||
52138ef3 | 358 | $self->NEXT::DISTINCT::method(); |
13021a80 JH |
359 | |
360 | rather than: | |
361 | ||
362 | $self->NEXT::method(); | |
363 | ||
52138ef3 JH |
364 | This causes the redispatcher to only visit each distinct C<method> method |
365 | once. That is, to skip any classes in the hierarchy that it has | |
366 | already visited during redispatch. So, for example, if the | |
13021a80 JH |
367 | previous example were rewritten: |
368 | ||
369 | package A; | |
52138ef3 | 370 | sub foo { print "called A::foo\n"; shift->NEXT::DISTINCT::foo() } |
13021a80 JH |
371 | |
372 | package B; | |
52138ef3 | 373 | sub foo { print "called B::foo\n"; shift->NEXT::DISTINCT::foo() } |
13021a80 JH |
374 | |
375 | package C; @ISA = qw( A ); | |
52138ef3 | 376 | sub foo { print "called C::foo\n"; shift->NEXT::DISTINCT::foo() } |
13021a80 JH |
377 | |
378 | package D; @ISA = qw(A B); | |
52138ef3 | 379 | sub foo { print "called D::foo\n"; shift->NEXT::DISTINCT::foo() } |
13021a80 JH |
380 | |
381 | package E; @ISA = qw(C D); | |
52138ef3 | 382 | sub foo { print "called E::foo\n"; shift->NEXT::DISTINCT::foo() } |
13021a80 JH |
383 | |
384 | E->foo(); | |
385 | ||
386 | then it would print: | |
387 | ||
388 | called E::foo | |
389 | called C::foo | |
390 | called A::foo | |
391 | called D::foo | |
392 | called B::foo | |
393 | ||
52138ef3 JH |
394 | and omit the second call to C<A::foo> (since it would not be distinct |
395 | from the first call to C<A::foo>). | |
13021a80 JH |
396 | |
397 | Note that you can also use: | |
398 | ||
52138ef3 | 399 | $self->NEXT::DISTINCT::ACTUAL::method(); |
13021a80 JH |
400 | |
401 | or: | |
402 | ||
52138ef3 | 403 | $self->NEXT::ACTUAL::DISTINCT::method(); |
e4783b1c | 404 | |
13021a80 | 405 | to get both unique invocation I<and> exception-on-failure. |
e4783b1c | 406 | |
52138ef3 JH |
407 | Note that, for historical compatibility, you can also use |
408 | C<NEXT::UNSEEN> instead of C<NEXT::DISTINCT>. | |
e4783b1c | 409 | |
bf5734d4 JH |
410 | |
411 | =head2 Invoking all versions of a method with a single call | |
412 | ||
413 | Yet another pseudo-class that NEXT.pm provides is C<EVERY>. | |
414 | Its behaviour is considerably simpler than that of the C<NEXT> family. | |
415 | A call to: | |
416 | ||
417 | $obj->EVERY::foo(); | |
418 | ||
419 | calls I<every> method named C<foo> that the object in C<$obj> has inherited. | |
420 | That is: | |
421 | ||
422 | use NEXT; | |
423 | ||
424 | package A; @ISA = qw(B D X); | |
425 | sub foo { print "A::foo " } | |
426 | ||
427 | package B; @ISA = qw(D X); | |
428 | sub foo { print "B::foo " } | |
429 | ||
430 | package X; @ISA = qw(D); | |
431 | sub foo { print "X::foo " } | |
432 | ||
433 | package D; | |
434 | sub foo { print "D::foo " } | |
435 | ||
436 | package main; | |
437 | ||
438 | my $obj = bless {}, 'A'; | |
439 | $obj->EVERY::foo(); # prints" A::foo B::foo X::foo D::foo | |
440 | ||
441 | Prefixing a method call with C<EVERY::> causes every method in the | |
442 | object's hierarchy with that name to be invoked. As the above example | |
443 | illustrates, they are not called in Perl's usual "left-most-depth-first" | |
444 | order. Instead, they are called "breadth-first-dependency-wise". | |
445 | ||
446 | That means that the inheritance tree of the object is traversed breadth-first | |
447 | and the resulting order of classes is used as the sequence in which methods | |
448 | are called. However, that sequence is modified by imposing a rule that the | |
3c4b39be | 449 | appropriate method of a derived class must be called before the same method of |
bf5734d4 JH |
450 | any ancestral class. That's why, in the above example, C<X::foo> is called |
451 | before C<D::foo>, even though C<D> comes before C<X> in C<@B::ISA>. | |
452 | ||
453 | In general, there's no need to worry about the order of calls. They will be | |
454 | left-to-right, breadth-first, most-derived-first. This works perfectly for | |
455 | most inherited methods (including destructors), but is inappropriate for | |
456 | some kinds of methods (such as constructors, cloners, debuggers, and | |
457 | initializers) where it's more appropriate that the least-derived methods be | |
458 | called first (as more-derived methods may rely on the behaviour of their | |
459 | "ancestors"). In that case, instead of using the C<EVERY> pseudo-class: | |
460 | ||
461 | $obj->EVERY::foo(); # prints" A::foo B::foo X::foo D::foo | |
462 | ||
463 | you can use the C<EVERY::LAST> pseudo-class: | |
464 | ||
465 | $obj->EVERY::LAST::foo(); # prints" D::foo X::foo B::foo A::foo | |
466 | ||
467 | which reverses the order of method call. | |
468 | ||
469 | Whichever version is used, the actual methods are called in the same | |
470 | context (list, scalar, or void) as the original call via C<EVERY>, and return: | |
471 | ||
472 | =over | |
473 | ||
474 | =item * | |
475 | ||
476 | A hash of array references in list context. Each entry of the hash has the | |
477 | fully qualified method name as its key and a reference to an array containing | |
478 | the method's list-context return values as its value. | |
479 | ||
480 | =item * | |
481 | ||
482 | A reference to a hash of scalar values in scalar context. Each entry of the hash has the | |
483 | fully qualified method name as its key and the method's scalar-context return values as its value. | |
484 | ||
485 | =item * | |
486 | ||
487 | Nothing in void context (obviously). | |
488 | ||
489 | =back | |
490 | ||
491 | =head2 Using C<EVERY> methods | |
492 | ||
493 | The typical way to use an C<EVERY> call is to wrap it in another base | |
494 | method, that all classes inherit. For example, to ensure that every | |
495 | destructor an object inherits is actually called (as opposed to just the | |
496 | left-most-depth-first-est one): | |
497 | ||
498 | package Base; | |
499 | sub DESTROY { $_[0]->EVERY::Destroy } | |
500 | ||
501 | package Derived1; | |
502 | use base 'Base'; | |
503 | sub Destroy {...} | |
504 | ||
505 | package Derived2; | |
506 | use base 'Base', 'Derived1'; | |
507 | sub Destroy {...} | |
508 | ||
509 | et cetera. Every derived class than needs its own clean-up | |
510 | behaviour simply adds its own C<Destroy> method (I<not> a C<DESTROY> method), | |
511 | which the call to C<EVERY::LAST::Destroy> in the inherited destructor | |
512 | then correctly picks up. | |
513 | ||
514 | Likewise, to create a class hierarchy in which every initializer inherited by | |
515 | a new object is invoked: | |
516 | ||
517 | package Base; | |
518 | sub new { | |
519 | my ($class, %args) = @_; | |
520 | my $obj = bless {}, $class; | |
521 | $obj->EVERY::LAST::Init(\%args); | |
522 | } | |
523 | ||
524 | package Derived1; | |
525 | use base 'Base'; | |
526 | sub Init { | |
527 | my ($argsref) = @_; | |
528 | ... | |
529 | } | |
530 | ||
531 | package Derived2; | |
532 | use base 'Base', 'Derived1'; | |
533 | sub Init { | |
534 | my ($argsref) = @_; | |
535 | ... | |
536 | } | |
537 | ||
538 | et cetera. Every derived class than needs some additional initialization | |
539 | behaviour simply adds its own C<Init> method (I<not> a C<new> method), | |
540 | which the call to C<EVERY::LAST::Init> in the inherited constructor | |
541 | then correctly picks up. | |
542 | ||
543 | ||
e4783b1c JH |
544 | =head1 AUTHOR |
545 | ||
546 | Damian Conway (damian@conway.org) | |
547 | ||
548 | =head1 BUGS AND IRRITATIONS | |
549 | ||
550 | Because it's a module, not an integral part of the interpreter, NEXT.pm | |
551 | has to guess where the surrounding call was found in the method | |
552 | look-up sequence. In the presence of diamond inheritance patterns | |
553 | it occasionally guesses wrong. | |
554 | ||
555 | It's also too slow (despite caching). | |
556 | ||
557 | Comment, suggestions, and patches welcome. | |
558 | ||
559 | =head1 COPYRIGHT | |
560 | ||
55a1c97c | 561 | Copyright (c) 2000-2001, Damian Conway. All Rights Reserved. |
e4783b1c | 562 | This module is free software. It may be used, redistributed |
55a1c97c | 563 | and/or modified under the same terms as Perl itself. |