Commit | Line | Data |
e4783b1c |
1 | package NEXT; |
3c2847f4 |
2 | $VERSION = '0.64'; |
e4783b1c |
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 |
11 | while (my $next = shift @inlist) { |
12 | push @outlist, $next; |
e4783b1c |
13 | no strict 'refs'; |
14 | unshift @inlist, @{"$outlist[-1]::ISA"}; |
15 | } |
16 | return @outlist; |
17 | } |
18 | |
bf5734d4 |
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 |
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 $NEXT::AUTOLOAD; |
3c2847f4 |
45 | my ($caller_class, $caller_method) = do { $caller =~ m{(.*)::(.*)}g }; |
46 | my ($wanted_class, $wanted_method) = do { $wanted =~ m{(.*)::(.*)}g }; |
597fc7a0 |
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 $caller_class |
62 | } |
63 | no strict 'refs'; |
082b74eb |
64 | @{$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 $wanted_method eq 'AUTOLOAD'; |
082b74eb |
71 | @{$NEXT::NEXT{$key,$wanted_method}} = |
72 | map { |
73 | my $stash = \%{"${_}::"}; |
74 | ($stash->{AUTOLOAD} && (*{$stash->{AUTOLOAD}}{CODE})) |
75 | ? "${_}::AUTOLOAD" |
76 | : () } @forebears |
597fc7a0 |
77 | unless @{$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 |
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 |
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 |
95 | if $wanted_method eq 'AUTOLOAD'; |
96 | $$call_method = $caller_class."::NEXT::".$wanted_method; |
97 | return $call_method->(@_); |
98 | }; |
e4783b1c |
99 | } |
100 | |
13021a80 |
101 | no strict 'vars'; |
597fc7a0 |
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 |
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 |
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..$#_]); |
178 | } |
179 | return; |
180 | } |
181 | }; |
bf5734d4 |
182 | } |
183 | |
597fc7a0 |
184 | package EVERY::LAST; @ISA = 'EVERY'; EVERY::ELSEWHERE::buildAUTOLOAD(); |
185 | package EVERY; @ISA = 'NEXT'; EVERY::ELSEWHERE::buildAUTOLOAD(); |
13021a80 |
186 | |
e4783b1c |
187 | 1; |
188 | |
189 | __END__ |
190 | |
191 | =head1 NAME |
192 | |
bf5734d4 |
193 | NEXT.pm - Provide a pseudo-class NEXT (et al) that allows method redispatch |
e4783b1c |
194 | |
195 | |
196 | =head1 SYNOPSIS |
197 | |
13021a80 |
198 | use NEXT; |
e4783b1c |
199 | |
13021a80 |
200 | package A; |
201 | sub A::method { print "$_[0]: A method\n"; $_[0]->NEXT::method() } |
202 | sub A::DESTROY { print "$_[0]: A dtor\n"; $_[0]->NEXT::DESTROY() } |
e4783b1c |
203 | |
13021a80 |
204 | package B; |
205 | use base qw( A ); |
206 | sub B::AUTOLOAD { print "$_[0]: B AUTOLOAD\n"; $_[0]->NEXT::AUTOLOAD() } |
207 | sub B::DESTROY { print "$_[0]: B dtor\n"; $_[0]->NEXT::DESTROY() } |
e4783b1c |
208 | |
13021a80 |
209 | package C; |
210 | sub C::method { print "$_[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"; $_[0]->NEXT::DESTROY() } |
e4783b1c |
213 | |
13021a80 |
214 | package D; |
215 | use base qw( B C ); |
216 | sub D::method { print "$_[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 |
224 | $obj->method(); # Calls D::method, A::method, C::method |
225 | $obj->missing_method(); # Calls D::AUTOLOAD, B::AUTOLOAD, C::AUTOLOAD |
e4783b1c |
226 | |
13021a80 |
227 | # Clean-up calls D::DESTROY, B::DESTROY, A::DESTROY, C::DESTROY |
e4783b1c |
228 | |
229 | |
bf5734d4 |
230 | |
e4783b1c |
231 | =head1 DESCRIPTION |
232 | |
233 | NEXT.pm adds a pseudoclass named C<NEXT> to any program |
e23eab12 |
234 | that uses it. If a method C<m> calls C<$self-E<gt>NEXT::m()>, the call to |
e4783b1c |
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<$self-E<gt>NEXT::m()> resumes the depth-first, |
55a1c97c |
238 | left-to-right search of C<$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 |
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 |
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 |
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 |
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 |
359 | |
360 | rather than: |
361 | |
362 | $self->NEXT::method(); |
363 | |
52138ef3 |
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 |
367 | previous example were rewritten: |
368 | |
369 | package A; |
52138ef3 |
370 | sub foo { print "called A::foo\n"; shift->NEXT::DISTINCT::foo() } |
13021a80 |
371 | |
372 | package B; |
52138ef3 |
373 | sub foo { print "called B::foo\n"; shift->NEXT::DISTINCT::foo() } |
13021a80 |
374 | |
375 | package C; @ISA = qw( A ); |
52138ef3 |
376 | sub foo { print "called C::foo\n"; shift->NEXT::DISTINCT::foo() } |
13021a80 |
377 | |
378 | package D; @ISA = qw(A B); |
52138ef3 |
379 | sub foo { print "called D::foo\n"; shift->NEXT::DISTINCT::foo() } |
13021a80 |
380 | |
381 | package E; @ISA = qw(C D); |
52138ef3 |
382 | sub foo { print "called E::foo\n"; shift->NEXT::DISTINCT::foo() } |
13021a80 |
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 |
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 |
396 | |
397 | Note that you can also use: |
398 | |
52138ef3 |
399 | $self->NEXT::DISTINCT::ACTUAL::method(); |
13021a80 |
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 |
407 | Note that, for historical compatibility, you can also use |
408 | C<NEXT::UNSEEN> instead of C<NEXT::DISTINCT>. |
e4783b1c |
409 | |
bf5734d4 |
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 |
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 |
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. |