1 | | | | package Exporter; |
2 | | | | |
3 | 1 | 0s | 0s | require 5.006; |
4 | | | | |
5 | | | | # Be lean. |
6 | | | | #use strict; |
7 | | | | #no strict 'refs'; |
8 | | | | |
9 | 1 | 0s | 0s | our $Debug = 0; |
10 | 1 | 0s | 0s | our $ExportLevel = 0; |
11 | 1 | 0s | 0s | our $Verbose ||= 0; |
12 | 1 | 0s | 0s | our $VERSION = '5.62'; |
13 | 1 | 0s | 0s | our (%Cache); |
14 | | | | # Carp does this now for us, so we can finally live w/o Carp |
15 | | | | #$Carp::Internal{Exporter} = 1; |
16 | | | | |
17 | | | | sub as_heavy { |
18 | | | | require Exporter::Heavy; |
19 | | | | # Unfortunately, this does not work if the caller is aliased as *name = \&foo |
20 | | | | # Thus the need to create a lot of identical subroutines |
21 | | | | my $c = (caller(1))[3]; |
22 | | | | $c =~ s/.*:://; |
23 | | | | \&{"Exporter::Heavy::heavy_$c"}; |
24 | | | | } |
25 | | | | |
26 | | | | sub export { |
27 | | | | goto &{as_heavy()}; |
28 | | | | } |
29 | | | | |
30 | | | | sub import { |
31 | | | | my $pkg = shift; |
32 | | | | my $callpkg = caller($ExportLevel); |
33 | | | | |
34 | | | | if ($pkg eq "Exporter" and @_ and $_[0] eq "import") { |
35 | | | | *{$callpkg."::import"} = \&import; |
36 | | | | return; |
37 | | | | } |
38 | | | | |
39 | | | | # We *need* to treat @{"$pkg\::EXPORT_FAIL"} since Carp uses it :-( |
40 | | | | my($exports, $fail) = (\@{"$pkg\::EXPORT"}, \@{"$pkg\::EXPORT_FAIL"}); |
41 | | | | return export $pkg, $callpkg, @_ |
42 | | | | if $Verbose or $Debug or @$fail > 1; |
43 | | | | my $export_cache = ($Cache{$pkg} ||= {}); |
44 | | | | my $args = @_ or @_ = @$exports; |
45 | | | | |
46 | | | | local $_; |
47 | | | | if ($args and not %$export_cache) { |
48 | | | | s/^&//, $export_cache->{$_} = 1 |
49 | | | | foreach (@$exports, @{"$pkg\::EXPORT_OK"}); |
50 | | | | } |
51 | | | | my $heavy; |
52 | | | | # Try very hard not to use {} and hence have to enter scope on the foreach |
53 | | | | # We bomb out of the loop with last as soon as heavy is set. |
54 | | | | if ($args or $fail) { |
55 | | | | ($heavy = (/\W/ or $args and not exists $export_cache->{$_} |
56 | | | | or @$fail and $_ eq $fail->[0])) and last |
57 | | | | foreach (@_); |
58 | | | | } else { |
59 | | | | ($heavy = /\W/) and last |
60 | | | | foreach (@_); |
61 | | | | } |
62 | | | | return export $pkg, $callpkg, ($args ? @_ : ()) if $heavy; |
63 | | | | local $SIG{__WARN__} = |
64 | | | | sub {require Carp; &Carp::carp}; |
65 | | | | # shortcut for the common case of no type character |
66 | | | | *{"$callpkg\::$_"} = \&{"$pkg\::$_"} foreach @_; |
67 | | | | } |
68 | | | | |
69 | | | | # Default methods |
70 | | | | |
71 | | | | sub export_fail { |
72 | | | | my $self = shift; |
73 | | | | @_; |
74 | | | | } |
75 | | | | |
76 | | | | # Unfortunately, caller(1)[3] "does not work" if the caller is aliased as |
77 | | | | # *name = \&foo. Thus the need to create a lot of identical subroutines |
78 | | | | # Otherwise we could have aliased them to export(). |
79 | | | | |
80 | | | | sub export_to_level { |
81 | | | | goto &{as_heavy()}; |
82 | | | | } |
83 | | | | |
84 | | | | sub export_tags { |
85 | | | | goto &{as_heavy()}; |
86 | | | | } |
87 | | | | |
88 | | | | sub export_ok_tags { |
89 | | | | goto &{as_heavy()}; |
90 | | | | } |
91 | | | | |
92 | | | | sub require_version { |
93 | | | | goto &{as_heavy()}; |
94 | | | | } |
95 | | | | |
96 | 1 | 0s | 0s | 1; |
97 | | | | __END__ |
98 | | | | |
99 | | | | =head1 NAME |
100 | | | | |
101 | | | | Exporter - Implements default import method for modules |
102 | | | | |
103 | | | | =head1 SYNOPSIS |
104 | | | | |
105 | | | | In module YourModule.pm: |
106 | | | | |
107 | | | | package YourModule; |
108 | | | | require Exporter; |
109 | | | | @ISA = qw(Exporter); |
110 | | | | @EXPORT_OK = qw(munge frobnicate); # symbols to export on request |
111 | | | | |
112 | | | | or |
113 | | | | |
114 | | | | package YourModule; |
115 | | | | use Exporter 'import'; # gives you Exporter's import() method directly |
116 | | | | @EXPORT_OK = qw(munge frobnicate); # symbols to export on request |
117 | | | | |
118 | | | | In other files which wish to use YourModule: |
119 | | | | |
120 | | | | use ModuleName qw(frobnicate); # import listed symbols |
121 | | | | frobnicate ($left, $right) # calls YourModule::frobnicate |
122 | | | | |
123 | | | | Take a look at L</Good Practices> for some variants |
124 | | | | you will like to use in modern Perl code. |
125 | | | | |
126 | | | | =head1 DESCRIPTION |
127 | | | | |
128 | | | | The Exporter module implements an C<import> method which allows a module |
129 | | | | to export functions and variables to its users' namespaces. Many modules |
130 | | | | use Exporter rather than implementing their own C<import> method because |
131 | | | | Exporter provides a highly flexible interface, with an implementation optimised |
132 | | | | for the common case. |
133 | | | | |
134 | | | | Perl automatically calls the C<import> method when processing a |
135 | | | | C<use> statement for a module. Modules and C<use> are documented |
136 | | | | in L<perlfunc> and L<perlmod>. Understanding the concept of |
137 | | | | modules and how the C<use> statement operates is important to |
138 | | | | understanding the Exporter. |
139 | | | | |
140 | | | | =head2 How to Export |
141 | | | | |
142 | | | | The arrays C<@EXPORT> and C<@EXPORT_OK> in a module hold lists of |
143 | | | | symbols that are going to be exported into the users name space by |
144 | | | | default, or which they can request to be exported, respectively. The |
145 | | | | symbols can represent functions, scalars, arrays, hashes, or typeglobs. |
146 | | | | The symbols must be given by full name with the exception that the |
147 | | | | ampersand in front of a function is optional, e.g. |
148 | | | | |
149 | | | | @EXPORT = qw(afunc $scalar @array); # afunc is a function |
150 | | | | @EXPORT_OK = qw(&bfunc %hash *typeglob); # explicit prefix on &bfunc |
151 | | | | |
152 | | | | If you are only exporting function names it is recommended to omit the |
153 | | | | ampersand, as the implementation is faster this way. |
154 | | | | |
155 | | | | =head2 Selecting What To Export |
156 | | | | |
157 | | | | Do B<not> export method names! |
158 | | | | |
159 | | | | Do B<not> export anything else by default without a good reason! |
160 | | | | |
161 | | | | Exports pollute the namespace of the module user. If you must export |
162 | | | | try to use @EXPORT_OK in preference to @EXPORT and avoid short or |
163 | | | | common symbol names to reduce the risk of name clashes. |
164 | | | | |
165 | | | | Generally anything not exported is still accessible from outside the |
166 | | | | module using the ModuleName::item_name (or $blessed_ref-E<gt>method) |
167 | | | | syntax. By convention you can use a leading underscore on names to |
168 | | | | informally indicate that they are 'internal' and not for public use. |
169 | | | | |
170 | | | | (It is actually possible to get private functions by saying: |
171 | | | | |
172 | | | | my $subref = sub { ... }; |
173 | | | | $subref->(@args); # Call it as a function |
174 | | | | $obj->$subref(@args); # Use it as a method |
175 | | | | |
176 | | | | However if you use them for methods it is up to you to figure out |
177 | | | | how to make inheritance work.) |
178 | | | | |
179 | | | | As a general rule, if the module is trying to be object oriented |
180 | | | | then export nothing. If it's just a collection of functions then |
181 | | | | @EXPORT_OK anything but use @EXPORT with caution. For function and |
182 | | | | method names use barewords in preference to names prefixed with |
183 | | | | ampersands for the export lists. |
184 | | | | |
185 | | | | Other module design guidelines can be found in L<perlmod>. |
186 | | | | |
187 | | | | =head2 How to Import |
188 | | | | |
189 | | | | In other files which wish to use your module there are three basic ways for |
190 | | | | them to load your module and import its symbols: |
191 | | | | |
192 | | | | =over 4 |
193 | | | | |
194 | | | | =item C<use ModuleName;> |
195 | | | | |
196 | | | | This imports all the symbols from ModuleName's @EXPORT into the namespace |
197 | | | | of the C<use> statement. |
198 | | | | |
199 | | | | =item C<use ModuleName ();> |
200 | | | | |
201 | | | | This causes perl to load your module but does not import any symbols. |
202 | | | | |
203 | | | | =item C<use ModuleName qw(...);> |
204 | | | | |
205 | | | | This imports only the symbols listed by the caller into their namespace. |
206 | | | | All listed symbols must be in your @EXPORT or @EXPORT_OK, else an error |
207 | | | | occurs. The advanced export features of Exporter are accessed like this, |
208 | | | | but with list entries that are syntactically distinct from symbol names. |
209 | | | | |
210 | | | | =back |
211 | | | | |
212 | | | | Unless you want to use its advanced features, this is probably all you |
213 | | | | need to know to use Exporter. |
214 | | | | |
215 | | | | =head1 Advanced features |
216 | | | | |
217 | | | | =head2 Specialised Import Lists |
218 | | | | |
219 | | | | If any of the entries in an import list begins with !, : or / then |
220 | | | | the list is treated as a series of specifications which either add to |
221 | | | | or delete from the list of names to import. They are processed left to |
222 | | | | right. Specifications are in the form: |
223 | | | | |
224 | | | | [!]name This name only |
225 | | | | [!]:DEFAULT All names in @EXPORT |
226 | | | | [!]:tag All names in $EXPORT_TAGS{tag} anonymous list |
227 | | | | [!]/pattern/ All names in @EXPORT and @EXPORT_OK which match |
228 | | | | |
229 | | | | A leading ! indicates that matching names should be deleted from the |
230 | | | | list of names to import. If the first specification is a deletion it |
231 | | | | is treated as though preceded by :DEFAULT. If you just want to import |
232 | | | | extra names in addition to the default set you will still need to |
233 | | | | include :DEFAULT explicitly. |
234 | | | | |
235 | | | | e.g., Module.pm defines: |
236 | | | | |
237 | | | | @EXPORT = qw(A1 A2 A3 A4 A5); |
238 | | | | @EXPORT_OK = qw(B1 B2 B3 B4 B5); |
239 | | | | %EXPORT_TAGS = (T1 => [qw(A1 A2 B1 B2)], T2 => [qw(A1 A2 B3 B4)]); |
240 | | | | |
241 | | | | Note that you cannot use tags in @EXPORT or @EXPORT_OK. |
242 | | | | Names in EXPORT_TAGS must also appear in @EXPORT or @EXPORT_OK. |
243 | | | | |
244 | | | | An application using Module can say something like: |
245 | | | | |
246 | | | | use Module qw(:DEFAULT :T2 !B3 A3); |
247 | | | | |
248 | | | | Other examples include: |
249 | | | | |
250 | | | | use Socket qw(!/^[AP]F_/ !SOMAXCONN !SOL_SOCKET); |
251 | | | | use POSIX qw(:errno_h :termios_h !TCSADRAIN !/^EXIT/); |
252 | | | | |
253 | | | | Remember that most patterns (using //) will need to be anchored |
254 | | | | with a leading ^, e.g., C</^EXIT/> rather than C</EXIT/>. |
255 | | | | |
256 | | | | You can say C<BEGIN { $Exporter::Verbose=1 }> to see how the |
257 | | | | specifications are being processed and what is actually being imported |
258 | | | | into modules. |
259 | | | | |
260 | | | | =head2 Exporting without using Exporter's import method |
261 | | | | |
262 | | | | Exporter has a special method, 'export_to_level' which is used in situations |
263 | | | | where you can't directly call Exporter's import method. The export_to_level |
264 | | | | method looks like: |
265 | | | | |
266 | | | | MyPackage->export_to_level($where_to_export, $package, @what_to_export); |
267 | | | | |
268 | | | | where $where_to_export is an integer telling how far up the calling stack |
269 | | | | to export your symbols, and @what_to_export is an array telling what |
270 | | | | symbols *to* export (usually this is @_). The $package argument is |
271 | | | | currently unused. |
272 | | | | |
273 | | | | For example, suppose that you have a module, A, which already has an |
274 | | | | import function: |
275 | | | | |
276 | | | | package A; |
277 | | | | |
278 | | | | @ISA = qw(Exporter); |
279 | | | | @EXPORT_OK = qw ($b); |
280 | | | | |
281 | | | | sub import |
282 | | | | { |
283 | | | | $A::b = 1; # not a very useful import method |
284 | | | | } |
285 | | | | |
286 | | | | and you want to Export symbol $A::b back to the module that called |
287 | | | | package A. Since Exporter relies on the import method to work, via |
288 | | | | inheritance, as it stands Exporter::import() will never get called. |
289 | | | | Instead, say the following: |
290 | | | | |
291 | | | | package A; |
292 | | | | @ISA = qw(Exporter); |
293 | | | | @EXPORT_OK = qw ($b); |
294 | | | | |
295 | | | | sub import |
296 | | | | { |
297 | | | | $A::b = 1; |
298 | | | | A->export_to_level(1, @_); |
299 | | | | } |
300 | | | | |
301 | | | | This will export the symbols one level 'above' the current package - ie: to |
302 | | | | the program or module that used package A. |
303 | | | | |
304 | | | | Note: Be careful not to modify C<@_> at all before you call export_to_level |
305 | | | | - or people using your package will get very unexplained results! |
306 | | | | |
307 | | | | =head2 Exporting without inheriting from Exporter |
308 | | | | |
309 | | | | By including Exporter in your @ISA you inherit an Exporter's import() method |
310 | | | | but you also inherit several other helper methods which you probably don't |
311 | | | | want. To avoid this you can do |
312 | | | | |
313 | | | | package YourModule; |
314 | | | | use Exporter qw( import ); |
315 | | | | |
316 | | | | which will export Exporter's own import() method into YourModule. |
317 | | | | Everything will work as before but you won't need to include Exporter in |
318 | | | | @YourModule::ISA. |
319 | | | | |
320 | | | | Note: This feature was introduced in version 5.57 |
321 | | | | of Exporter, released with perl 5.8.3. |
322 | | | | |
323 | | | | =head2 Module Version Checking |
324 | | | | |
325 | | | | The Exporter module will convert an attempt to import a number from a |
326 | | | | module into a call to $module_name-E<gt>require_version($value). This can |
327 | | | | be used to validate that the version of the module being used is |
328 | | | | greater than or equal to the required version. |
329 | | | | |
330 | | | | The Exporter module supplies a default require_version method which |
331 | | | | checks the value of $VERSION in the exporting module. |
332 | | | | |
333 | | | | Since the default require_version method treats the $VERSION number as |
334 | | | | a simple numeric value it will regard version 1.10 as lower than |
335 | | | | 1.9. For this reason it is strongly recommended that you use numbers |
336 | | | | with at least two decimal places, e.g., 1.09. |
337 | | | | |
338 | | | | =head2 Managing Unknown Symbols |
339 | | | | |
340 | | | | In some situations you may want to prevent certain symbols from being |
341 | | | | exported. Typically this applies to extensions which have functions |
342 | | | | or constants that may not exist on some systems. |
343 | | | | |
344 | | | | The names of any symbols that cannot be exported should be listed |
345 | | | | in the C<@EXPORT_FAIL> array. |
346 | | | | |
347 | | | | If a module attempts to import any of these symbols the Exporter |
348 | | | | will give the module an opportunity to handle the situation before |
349 | | | | generating an error. The Exporter will call an export_fail method |
350 | | | | with a list of the failed symbols: |
351 | | | | |
352 | | | | @failed_symbols = $module_name->export_fail(@failed_symbols); |
353 | | | | |
354 | | | | If the export_fail method returns an empty list then no error is |
355 | | | | recorded and all the requested symbols are exported. If the returned |
356 | | | | list is not empty then an error is generated for each symbol and the |
357 | | | | export fails. The Exporter provides a default export_fail method which |
358 | | | | simply returns the list unchanged. |
359 | | | | |
360 | | | | Uses for the export_fail method include giving better error messages |
361 | | | | for some symbols and performing lazy architectural checks (put more |
362 | | | | symbols into @EXPORT_FAIL by default and then take them out if someone |
363 | | | | actually tries to use them and an expensive check shows that they are |
364 | | | | usable on that platform). |
365 | | | | |
366 | | | | =head2 Tag Handling Utility Functions |
367 | | | | |
368 | | | | Since the symbols listed within %EXPORT_TAGS must also appear in either |
369 | | | | @EXPORT or @EXPORT_OK, two utility functions are provided which allow |
370 | | | | you to easily add tagged sets of symbols to @EXPORT or @EXPORT_OK: |
371 | | | | |
372 | | | | %EXPORT_TAGS = (foo => [qw(aa bb cc)], bar => [qw(aa cc dd)]); |
373 | | | | |
374 | | | | Exporter::export_tags('foo'); # add aa, bb and cc to @EXPORT |
375 | | | | Exporter::export_ok_tags('bar'); # add aa, cc and dd to @EXPORT_OK |
376 | | | | |
377 | | | | Any names which are not tags are added to @EXPORT or @EXPORT_OK |
378 | | | | unchanged but will trigger a warning (with C<-w>) to avoid misspelt tags |
379 | | | | names being silently added to @EXPORT or @EXPORT_OK. Future versions |
380 | | | | may make this a fatal error. |
381 | | | | |
382 | | | | =head2 Generating combined tags |
383 | | | | |
384 | | | | If several symbol categories exist in %EXPORT_TAGS, it's usually |
385 | | | | useful to create the utility ":all" to simplify "use" statements. |
386 | | | | |
387 | | | | The simplest way to do this is: |
388 | | | | |
389 | | | | %EXPORT_TAGS = (foo => [qw(aa bb cc)], bar => [qw(aa cc dd)]); |
390 | | | | |
391 | | | | # add all the other ":class" tags to the ":all" class, |
392 | | | | # deleting duplicates |
393 | | | | { |
394 | | | | my %seen; |
395 | | | | |
396 | | | | push @{$EXPORT_TAGS{all}}, |
397 | | | | grep {!$seen{$_}++} @{$EXPORT_TAGS{$_}} foreach keys %EXPORT_TAGS; |
398 | | | | } |
399 | | | | |
400 | | | | CGI.pm creates an ":all" tag which contains some (but not really |
401 | | | | all) of its categories. That could be done with one small |
402 | | | | change: |
403 | | | | |
404 | | | | # add some of the other ":class" tags to the ":all" class, |
405 | | | | # deleting duplicates |
406 | | | | { |
407 | | | | my %seen; |
408 | | | | |
409 | | | | push @{$EXPORT_TAGS{all}}, |
410 | | | | grep {!$seen{$_}++} @{$EXPORT_TAGS{$_}} |
411 | | | | foreach qw/html2 html3 netscape form cgi internal/; |
412 | | | | } |
413 | | | | |
414 | | | | Note that the tag names in %EXPORT_TAGS don't have the leading ':'. |
415 | | | | |
416 | | | | =head2 C<AUTOLOAD>ed Constants |
417 | | | | |
418 | | | | Many modules make use of C<AUTOLOAD>ing for constant subroutines to |
419 | | | | avoid having to compile and waste memory on rarely used values (see |
420 | | | | L<perlsub> for details on constant subroutines). Calls to such |
421 | | | | constant subroutines are not optimized away at compile time because |
422 | | | | they can't be checked at compile time for constancy. |
423 | | | | |
424 | | | | Even if a prototype is available at compile time, the body of the |
425 | | | | subroutine is not (it hasn't been C<AUTOLOAD>ed yet). perl needs to |
426 | | | | examine both the C<()> prototype and the body of a subroutine at |
427 | | | | compile time to detect that it can safely replace calls to that |
428 | | | | subroutine with the constant value. |
429 | | | | |
430 | | | | A workaround for this is to call the constants once in a C<BEGIN> block: |
431 | | | | |
432 | | | | package My ; |
433 | | | | |
434 | | | | use Socket ; |
435 | | | | |
436 | | | | foo( SO_LINGER ); ## SO_LINGER NOT optimized away; called at runtime |
437 | | | | BEGIN { SO_LINGER } |
438 | | | | foo( SO_LINGER ); ## SO_LINGER optimized away at compile time. |
439 | | | | |
440 | | | | This forces the C<AUTOLOAD> for C<SO_LINGER> to take place before |
441 | | | | SO_LINGER is encountered later in C<My> package. |
442 | | | | |
443 | | | | If you are writing a package that C<AUTOLOAD>s, consider forcing |
444 | | | | an C<AUTOLOAD> for any constants explicitly imported by other packages |
445 | | | | or which are usually used when your package is C<use>d. |
446 | | | | |
447 | | | | =head1 Good Practices |
448 | | | | |
449 | | | | =head2 Declaring C<@EXPORT_OK> and Friends |
450 | | | | |
451 | | | | When using C<Exporter> with the standard C<strict> and C<warnings> |
452 | | | | pragmas, the C<our> keyword is needed to declare the package |
453 | | | | variables C<@EXPORT_OK>, C<@EXPORT>, C<@ISA>, etc. |
454 | | | | |
455 | | | | our @ISA = qw(Exporter); |
456 | | | | our @EXPORT_OK = qw(munge frobnicate); |
457 | | | | |
458 | | | | If backward compatibility for Perls under 5.6 is important, |
459 | | | | one must write instead a C<use vars> statement. |
460 | | | | |
461 | | | | use vars qw(@ISA @EXPORT_OK); |
462 | | | | @ISA = qw(Exporter); |
463 | | | | @EXPORT_OK = qw(munge frobnicate); |
464 | | | | |
465 | | | | =head2 Playing Safe |
466 | | | | |
467 | | | | There are some caveats with the use of runtime statements |
468 | | | | like C<require Exporter> and the assignment to package |
469 | | | | variables, which can very subtle for the unaware programmer. |
470 | | | | This may happen for instance with mutually recursive |
471 | | | | modules, which are affected by the time the relevant |
472 | | | | constructions are executed. |
473 | | | | |
474 | | | | The ideal (but a bit ugly) way to never have to think |
475 | | | | about that is to use C<BEGIN> blocks. So the first part |
476 | | | | of the L</SYNOPSIS> code could be rewritten as: |
477 | | | | |
478 | | | | package YourModule; |
479 | | | | |
480 | | | | use strict; |
481 | | | | use warnings; |
482 | | | | |
483 | | | | our (@ISA, @EXPORT_OK); |
484 | | | | BEGIN { |
485 | | | | require Exporter; |
486 | | | | @ISA = qw(Exporter); |
487 | | | | @EXPORT_OK = qw(munge frobnicate); # symbols to export on request |
488 | | | | } |
489 | | | | |
490 | | | | The C<BEGIN> will assure that the loading of F<Exporter.pm> |
491 | | | | and the assignments to C<@ISA> and C<@EXPORT_OK> happen |
492 | | | | immediately, leaving no room for something to get awry |
493 | | | | or just plain wrong. |
494 | | | | |
495 | | | | With respect to loading C<Exporter> and inheriting, there |
496 | | | | are alternatives with the use of modules like C<base> and C<parent>. |
497 | | | | |
498 | | | | use base qw( Exporter ); |
499 | | | | # or |
500 | | | | use parent qw( Exporter ); |
501 | | | | |
502 | | | | Any of these statements are nice replacements for |
503 | | | | C<BEGIN { require Exporter; @ISA = qw(Exporter); }> |
504 | | | | with the same compile-time effect. The basic difference |
505 | | | | is that C<base> code interacts with declared C<fields> |
506 | | | | while C<parent> is a streamlined version of the older |
507 | | | | C<base> code to just establish the IS-A relationship. |
508 | | | | |
509 | | | | For more details, see the documentation and code of |
510 | | | | L<base> and L<parent>. |
511 | | | | |
512 | | | | Another thorough remedy to that runtime vs. |
513 | | | | compile-time trap is to use L<Exporter::Easy>, |
514 | | | | which is a wrapper of Exporter that allows all |
515 | | | | boilerplate code at a single gulp in the |
516 | | | | use statement. |
517 | | | | |
518 | | | | use Exporter::Easy ( |
519 | | | | OK => [ qw(munge frobnicate) ], |
520 | | | | ); |
521 | | | | # @ISA setup is automatic |
522 | | | | # all assignments happen at compile time |
523 | | | | |
524 | | | | =head2 What not to Export |
525 | | | | |
526 | | | | You have been warned already in L</Selecting What To Export> |
527 | | | | to not export: |
528 | | | | |
529 | | | | =over 4 |
530 | | | | |
531 | | | | =item * |
532 | | | | |
533 | | | | method names (because you don't need to |
534 | | | | and that's likely to not do what you want), |
535 | | | | |
536 | | | | =item * |
537 | | | | |
538 | | | | anything by default (because you don't want to surprise your users... |
539 | | | | badly) |
540 | | | | |
541 | | | | =item * |
542 | | | | |
543 | | | | anything you don't need to (because less is more) |
544 | | | | |
545 | | | | =back |
546 | | | | |
547 | | | | There's one more item to add to this list. Do B<not> |
548 | | | | export variable names. Just because C<Exporter> lets you |
549 | | | | do that, it does not mean you should. |
550 | | | | |
551 | | | | @EXPORT_OK = qw( $svar @avar %hvar ); # DON'T! |
552 | | | | |
553 | | | | Exporting variables is not a good idea. They can |
554 | | | | change under the hood, provoking horrible |
555 | | | | effects at-a-distance, that are too hard to track |
556 | | | | and to fix. Trust me: they are not worth it. |
557 | | | | |
558 | | | | To provide the capability to set/get class-wide |
559 | | | | settings, it is best instead to provide accessors |
560 | | | | as subroutines or class methods instead. |
561 | | | | |
562 | | | | =head1 SEE ALSO |
563 | | | | |
564 | | | | C<Exporter> is definitely not the only module with |
565 | | | | symbol exporter capabilities. At CPAN, you may find |
566 | | | | a bunch of them. Some are lighter. Some |
567 | | | | provide improved APIs and features. Peek the one |
568 | | | | that fits your needs. The following is |
569 | | | | a sample list of such modules. |
570 | | | | |
571 | | | | Exporter::Easy |
572 | | | | Exporter::Lite |
573 | | | | Exporter::Renaming |
574 | | | | Exporter::Tidy |
575 | | | | Sub::Exporter / Sub::Installer |
576 | | | | Perl6::Export / Perl6::Export::Attrs |
577 | | | | |
578 | | | | =head1 LICENSE |
579 | | | | |
580 | | | | This library is free software. You can redistribute it |
581 | | | | and/or modify it under the same terms as Perl itself. |
582 | | | | |
583 | | | | =cut |