Commit | Line | Data |
8990e307 |
1 | package Exporter; |
2 | |
732bb7c2 |
3 | require 5.006; |
8990e307 |
4 | |
0e57b4e8 |
5 | # Be lean. |
6 | #use strict; |
7 | #no strict 'refs'; |
b75c8c73 |
8 | |
9 | our $Debug = 0; |
10 | our $ExportLevel = 0; |
11 | our $Verbose ||= 0; |
3e927c50 |
12 | our $VERSION = '5.63'; |
a6faae8d |
13 | our (%Cache); |
3e927c50 |
14 | |
15 | # Carp 1.05+ does this now for us, but we may be running with an old Carp |
16 | $Carp::Internal{Exporter}++; |
2b5b2650 |
17 | |
0e57b4e8 |
18 | sub as_heavy { |
4af1b167 |
19 | require Exporter::Heavy; |
0e57b4e8 |
20 | # Unfortunately, this does not work if the caller is aliased as *name = \&foo |
21 | # Thus the need to create a lot of identical subroutines |
22 | my $c = (caller(1))[3]; |
23 | $c =~ s/.*:://; |
24 | \&{"Exporter::Heavy::heavy_$c"}; |
84902520 |
25 | } |
26 | |
4af1b167 |
27 | sub export { |
0e57b4e8 |
28 | goto &{as_heavy()}; |
a0d0e21e |
29 | } |
30 | |
4af1b167 |
31 | sub import { |
32 | my $pkg = shift; |
33 | my $callpkg = caller($ExportLevel); |
b75c8c73 |
34 | |
fe43f860 |
35 | if ($pkg eq "Exporter" and @_ and $_[0] eq "import") { |
36 | *{$callpkg."::import"} = \&import; |
37 | return; |
38 | } |
39 | |
4af1b167 |
40 | # We *need* to treat @{"$pkg\::EXPORT_FAIL"} since Carp uses it :-( |
a6faae8d |
41 | my($exports, $fail) = (\@{"$pkg\::EXPORT"}, \@{"$pkg\::EXPORT_FAIL"}); |
4af1b167 |
42 | return export $pkg, $callpkg, @_ |
b75c8c73 |
43 | if $Verbose or $Debug or @$fail > 1; |
a6faae8d |
44 | my $export_cache = ($Cache{$pkg} ||= {}); |
b75c8c73 |
45 | my $args = @_ or @_ = @$exports; |
732bb7c2 |
46 | |
47 | local $_; |
b75c8c73 |
48 | if ($args and not %$export_cache) { |
732bb7c2 |
49 | s/^&//, $export_cache->{$_} = 1 |
50 | foreach (@$exports, @{"$pkg\::EXPORT_OK"}); |
4af1b167 |
51 | } |
fa1bb02f |
52 | my $heavy; |
53 | # Try very hard not to use {} and hence have to enter scope on the foreach |
54 | # We bomb out of the loop with last as soon as heavy is set. |
55 | if ($args or $fail) { |
732bb7c2 |
56 | ($heavy = (/\W/ or $args and not exists $export_cache->{$_} |
fa1bb02f |
57 | or @$fail and $_ eq $fail->[0])) and last |
58 | foreach (@_); |
59 | } else { |
60 | ($heavy = /\W/) and last |
732bb7c2 |
61 | foreach (@_); |
4af1b167 |
62 | } |
732bb7c2 |
63 | return export $pkg, $callpkg, ($args ? @_ : ()) if $heavy; |
4af1b167 |
64 | local $SIG{__WARN__} = |
bb2cbcd1 |
65 | sub {require Carp; &Carp::carp}; |
732bb7c2 |
66 | # shortcut for the common case of no type character |
67 | *{"$callpkg\::$_"} = \&{"$pkg\::$_"} foreach @_; |
e50aee73 |
68 | } |
69 | |
b75c8c73 |
70 | # Default methods |
71 | |
2b5b2650 |
72 | sub export_fail { |
b75c8c73 |
73 | my $self = shift; |
74 | @_; |
2b5b2650 |
75 | } |
76 | |
0e57b4e8 |
77 | # Unfortunately, caller(1)[3] "does not work" if the caller is aliased as |
78 | # *name = \&foo. Thus the need to create a lot of identical subroutines |
79 | # Otherwise we could have aliased them to export(). |
b75c8c73 |
80 | |
0e57b4e8 |
81 | sub export_to_level { |
82 | goto &{as_heavy()}; |
83 | } |
84 | |
85 | sub export_tags { |
86 | goto &{as_heavy()}; |
b75c8c73 |
87 | } |
88 | |
0e57b4e8 |
89 | sub export_ok_tags { |
90 | goto &{as_heavy()}; |
91 | } |
92 | |
93 | sub require_version { |
94 | goto &{as_heavy()}; |
95 | } |
b75c8c73 |
96 | |
2b5b2650 |
97 | 1; |
732bb7c2 |
98 | __END__ |
b75c8c73 |
99 | |
2b5b2650 |
100 | =head1 NAME |
101 | |
102 | Exporter - Implements default import method for modules |
103 | |
104 | =head1 SYNOPSIS |
105 | |
3e927c50 |
106 | In module F<YourModule.pm>: |
2b5b2650 |
107 | |
65503211 |
108 | package YourModule; |
2b5b2650 |
109 | require Exporter; |
110 | @ISA = qw(Exporter); |
65503211 |
111 | @EXPORT_OK = qw(munge frobnicate); # symbols to export on request |
2b5b2650 |
112 | |
fe43f860 |
113 | or |
114 | |
115 | package YourModule; |
116 | use Exporter 'import'; # gives you Exporter's import() method directly |
117 | @EXPORT_OK = qw(munge frobnicate); # symbols to export on request |
118 | |
3e927c50 |
119 | In other files which wish to use C<YourModule>: |
2b5b2650 |
120 | |
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121 | use YourModule qw(frobnicate); # import listed symbols |
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122 | frobnicate ($left, $right) # calls YourModule::frobnicate |
2b5b2650 |
123 | |
47f97feb |
124 | Take a look at L</Good Practices> for some variants |
125 | you will like to use in modern Perl code. |
126 | |
2b5b2650 |
127 | =head1 DESCRIPTION |
128 | |
65503211 |
129 | The Exporter module implements an C<import> method which allows a module |
130 | to export functions and variables to its users' namespaces. Many modules |
131 | use Exporter rather than implementing their own C<import> method because |
132 | Exporter provides a highly flexible interface, with an implementation optimised |
133 | for the common case. |
2b5b2650 |
134 | |
135 | Perl automatically calls the C<import> method when processing a |
136 | C<use> statement for a module. Modules and C<use> are documented |
137 | in L<perlfunc> and L<perlmod>. Understanding the concept of |
138 | modules and how the C<use> statement operates is important to |
139 | understanding the Exporter. |
140 | |
4fddf32b |
141 | =head2 How to Export |
142 | |
143 | The arrays C<@EXPORT> and C<@EXPORT_OK> in a module hold lists of |
144 | symbols that are going to be exported into the users name space by |
145 | default, or which they can request to be exported, respectively. The |
146 | symbols can represent functions, scalars, arrays, hashes, or typeglobs. |
147 | The symbols must be given by full name with the exception that the |
148 | ampersand in front of a function is optional, e.g. |
149 | |
150 | @EXPORT = qw(afunc $scalar @array); # afunc is a function |
151 | @EXPORT_OK = qw(&bfunc %hash *typeglob); # explicit prefix on &bfunc |
152 | |
65503211 |
153 | If you are only exporting function names it is recommended to omit the |
154 | ampersand, as the implementation is faster this way. |
155 | |
2b5b2650 |
156 | =head2 Selecting What To Export |
157 | |
158 | Do B<not> export method names! |
159 | |
160 | Do B<not> export anything else by default without a good reason! |
161 | |
162 | Exports pollute the namespace of the module user. If you must export |
3e927c50 |
163 | try to use C<@EXPORT_OK> in preference to C<@EXPORT> and avoid short or |
2b5b2650 |
164 | common symbol names to reduce the risk of name clashes. |
165 | |
166 | Generally anything not exported is still accessible from outside the |
3e927c50 |
167 | module using the C<YourModule::item_name> (or C<< $blessed_ref->method >>) |
2b5b2650 |
168 | syntax. By convention you can use a leading underscore on names to |
169 | informally indicate that they are 'internal' and not for public use. |
170 | |
171 | (It is actually possible to get private functions by saying: |
172 | |
173 | my $subref = sub { ... }; |
e60ce172 |
174 | $subref->(@args); # Call it as a function |
175 | $obj->$subref(@args); # Use it as a method |
2b5b2650 |
176 | |
e60ce172 |
177 | However if you use them for methods it is up to you to figure out |
178 | how to make inheritance work.) |
2b5b2650 |
179 | |
180 | As a general rule, if the module is trying to be object oriented |
181 | then export nothing. If it's just a collection of functions then |
3e927c50 |
182 | C<@EXPORT_OK> anything but use C<@EXPORT> with caution. For function and |
65503211 |
183 | method names use barewords in preference to names prefixed with |
184 | ampersands for the export lists. |
2b5b2650 |
185 | |
186 | Other module design guidelines can be found in L<perlmod>. |
187 | |
65503211 |
188 | =head2 How to Import |
189 | |
190 | In other files which wish to use your module there are three basic ways for |
191 | them to load your module and import its symbols: |
192 | |
193 | =over 4 |
194 | |
3e927c50 |
195 | =item C<use YourModule;> |
65503211 |
196 | |
3e927c50 |
197 | This imports all the symbols from YourModule's C<@EXPORT> into the namespace |
65503211 |
198 | of the C<use> statement. |
199 | |
3e927c50 |
200 | =item C<use YourModule ();> |
65503211 |
201 | |
202 | This causes perl to load your module but does not import any symbols. |
203 | |
3e927c50 |
204 | =item C<use YourModule qw(...);> |
65503211 |
205 | |
206 | This imports only the symbols listed by the caller into their namespace. |
3e927c50 |
207 | All listed symbols must be in your C<@EXPORT> or C<@EXPORT_OK>, else an error |
65503211 |
208 | occurs. The advanced export features of Exporter are accessed like this, |
209 | but with list entries that are syntactically distinct from symbol names. |
210 | |
211 | =back |
212 | |
213 | Unless you want to use its advanced features, this is probably all you |
214 | need to know to use Exporter. |
215 | |
216 | =head1 Advanced features |
217 | |
2b5b2650 |
218 | =head2 Specialised Import Lists |
219 | |
a29b0897 |
220 | If any of the entries in an import list begins with !, : or / then |
221 | the list is treated as a series of specifications which either add to |
222 | or delete from the list of names to import. They are processed left to |
2b5b2650 |
223 | right. Specifications are in the form: |
224 | |
225 | [!]name This name only |
226 | [!]:DEFAULT All names in @EXPORT |
227 | [!]:tag All names in $EXPORT_TAGS{tag} anonymous list |
228 | [!]/pattern/ All names in @EXPORT and @EXPORT_OK which match |
229 | |
230 | A leading ! indicates that matching names should be deleted from the |
231 | list of names to import. If the first specification is a deletion it |
232 | is treated as though preceded by :DEFAULT. If you just want to import |
233 | extra names in addition to the default set you will still need to |
234 | include :DEFAULT explicitly. |
235 | |
3e927c50 |
236 | e.g., F<Module.pm> defines: |
2b5b2650 |
237 | |
238 | @EXPORT = qw(A1 A2 A3 A4 A5); |
239 | @EXPORT_OK = qw(B1 B2 B3 B4 B5); |
240 | %EXPORT_TAGS = (T1 => [qw(A1 A2 B1 B2)], T2 => [qw(A1 A2 B3 B4)]); |
241 | |
242 | Note that you cannot use tags in @EXPORT or @EXPORT_OK. |
243 | Names in EXPORT_TAGS must also appear in @EXPORT or @EXPORT_OK. |
244 | |
245 | An application using Module can say something like: |
246 | |
247 | use Module qw(:DEFAULT :T2 !B3 A3); |
248 | |
249 | Other examples include: |
250 | |
251 | use Socket qw(!/^[AP]F_/ !SOMAXCONN !SOL_SOCKET); |
252 | use POSIX qw(:errno_h :termios_h !TCSADRAIN !/^EXIT/); |
253 | |
254 | Remember that most patterns (using //) will need to be anchored |
255 | with a leading ^, e.g., C</^EXIT/> rather than C</EXIT/>. |
256 | |
257 | You can say C<BEGIN { $Exporter::Verbose=1 }> to see how the |
258 | specifications are being processed and what is actually being imported |
259 | into modules. |
260 | |
65503211 |
261 | =head2 Exporting without using Exporter's import method |
84902520 |
262 | |
263 | Exporter has a special method, 'export_to_level' which is used in situations |
65503211 |
264 | where you can't directly call Exporter's import method. The export_to_level |
84902520 |
265 | method looks like: |
266 | |
cec46e5a |
267 | MyPackage->export_to_level($where_to_export, $package, @what_to_export); |
84902520 |
268 | |
3e927c50 |
269 | where C<$where_to_export> is an integer telling how far up the calling stack |
270 | to export your symbols, and C<@what_to_export> is an array telling what |
271 | symbols *to* export (usually this is C<@_>). The C<$package> argument is |
ba5725f8 |
272 | currently unused. |
84902520 |
273 | |
274 | For example, suppose that you have a module, A, which already has an |
275 | import function: |
276 | |
cec46e5a |
277 | package A; |
84902520 |
278 | |
cec46e5a |
279 | @ISA = qw(Exporter); |
280 | @EXPORT_OK = qw ($b); |
84902520 |
281 | |
cec46e5a |
282 | sub import |
283 | { |
284 | $A::b = 1; # not a very useful import method |
285 | } |
84902520 |
286 | |
3e927c50 |
287 | and you want to Export symbol C<$A::b> back to the module that called |
84902520 |
288 | package A. Since Exporter relies on the import method to work, via |
289 | inheritance, as it stands Exporter::import() will never get called. |
290 | Instead, say the following: |
291 | |
cec46e5a |
292 | package A; |
293 | @ISA = qw(Exporter); |
294 | @EXPORT_OK = qw ($b); |
84902520 |
295 | |
cec46e5a |
296 | sub import |
297 | { |
298 | $A::b = 1; |
299 | A->export_to_level(1, @_); |
300 | } |
84902520 |
301 | |
302 | This will export the symbols one level 'above' the current package - ie: to |
303 | the program or module that used package A. |
304 | |
fe43f860 |
305 | Note: Be careful not to modify C<@_> at all before you call export_to_level |
84902520 |
306 | - or people using your package will get very unexplained results! |
307 | |
fe43f860 |
308 | =head2 Exporting without inheriting from Exporter |
309 | |
3e927c50 |
310 | By including Exporter in your C<@ISA> you inherit an Exporter's import() method |
fe43f860 |
311 | but you also inherit several other helper methods which you probably don't |
312 | want. To avoid this you can do |
313 | |
314 | package YourModule; |
315 | use Exporter qw( import ); |
316 | |
317 | which will export Exporter's own import() method into YourModule. |
318 | Everything will work as before but you won't need to include Exporter in |
3e927c50 |
319 | C<@YourModule::ISA>. |
84902520 |
320 | |
47f97feb |
321 | Note: This feature was introduced in version 5.57 |
322 | of Exporter, released with perl 5.8.3. |
323 | |
2b5b2650 |
324 | =head2 Module Version Checking |
325 | |
326 | The Exporter module will convert an attempt to import a number from a |
3e927c50 |
327 | module into a call to C<< $module_name->require_version($value) >>. This can |
2b5b2650 |
328 | be used to validate that the version of the module being used is |
329 | greater than or equal to the required version. |
330 | |
3e927c50 |
331 | The Exporter module supplies a default C<require_version> method which |
332 | checks the value of C<$VERSION> in the exporting module. |
2b5b2650 |
333 | |
3e927c50 |
334 | Since the default C<require_version> method treats the C<$VERSION> number as |
d5e40bcc |
335 | a simple numeric value it will regard version 1.10 as lower than |
336 | 1.9. For this reason it is strongly recommended that you use numbers |
337 | with at least two decimal places, e.g., 1.09. |
2b5b2650 |
338 | |
339 | =head2 Managing Unknown Symbols |
340 | |
341 | In some situations you may want to prevent certain symbols from being |
342 | exported. Typically this applies to extensions which have functions |
343 | or constants that may not exist on some systems. |
344 | |
345 | The names of any symbols that cannot be exported should be listed |
346 | in the C<@EXPORT_FAIL> array. |
347 | |
7a2e2cd6 |
348 | If a module attempts to import any of these symbols the Exporter |
2b5b2650 |
349 | will give the module an opportunity to handle the situation before |
350 | generating an error. The Exporter will call an export_fail method |
351 | with a list of the failed symbols: |
352 | |
353 | @failed_symbols = $module_name->export_fail(@failed_symbols); |
354 | |
3e927c50 |
355 | If the C<export_fail> method returns an empty list then no error is |
2b5b2650 |
356 | recorded and all the requested symbols are exported. If the returned |
357 | list is not empty then an error is generated for each symbol and the |
3e927c50 |
358 | export fails. The Exporter provides a default C<export_fail> method which |
2b5b2650 |
359 | simply returns the list unchanged. |
360 | |
3e927c50 |
361 | Uses for the C<export_fail> method include giving better error messages |
2b5b2650 |
362 | for some symbols and performing lazy architectural checks (put more |
3e927c50 |
363 | symbols into C<@EXPORT_FAIL> by default and then take them out if someone |
2b5b2650 |
364 | actually tries to use them and an expensive check shows that they are |
365 | usable on that platform). |
366 | |
367 | =head2 Tag Handling Utility Functions |
368 | |
3e927c50 |
369 | Since the symbols listed within C<%EXPORT_TAGS> must also appear in either |
370 | C<@EXPORT> or C<@EXPORT_OK>, two utility functions are provided which allow |
371 | you to easily add tagged sets of symbols to C<@EXPORT> or C<@EXPORT_OK>: |
2b5b2650 |
372 | |
373 | %EXPORT_TAGS = (foo => [qw(aa bb cc)], bar => [qw(aa cc dd)]); |
374 | |
375 | Exporter::export_tags('foo'); # add aa, bb and cc to @EXPORT |
376 | Exporter::export_ok_tags('bar'); # add aa, cc and dd to @EXPORT_OK |
377 | |
3e927c50 |
378 | Any names which are not tags are added to C<@EXPORT> or C<@EXPORT_OK> |
d5e40bcc |
379 | unchanged but will trigger a warning (with C<-w>) to avoid misspelt tags |
3e927c50 |
380 | names being silently added to C<@EXPORT> or C<@EXPORT_OK>. Future versions |
2b5b2650 |
381 | may make this a fatal error. |
382 | |
d584343b |
383 | =head2 Generating combined tags |
384 | |
3e927c50 |
385 | If several symbol categories exist in C<%EXPORT_TAGS>, it's usually |
d584343b |
386 | useful to create the utility ":all" to simplify "use" statements. |
387 | |
388 | The simplest way to do this is: |
389 | |
390 | %EXPORT_TAGS = (foo => [qw(aa bb cc)], bar => [qw(aa cc dd)]); |
391 | |
392 | # add all the other ":class" tags to the ":all" class, |
393 | # deleting duplicates |
394 | { |
395 | my %seen; |
396 | |
397 | push @{$EXPORT_TAGS{all}}, |
398 | grep {!$seen{$_}++} @{$EXPORT_TAGS{$_}} foreach keys %EXPORT_TAGS; |
399 | } |
400 | |
3e927c50 |
401 | F<CGI.pm> creates an ":all" tag which contains some (but not really |
d584343b |
402 | all) of its categories. That could be done with one small |
403 | change: |
404 | |
405 | # add some of the other ":class" tags to the ":all" class, |
406 | # deleting duplicates |
407 | { |
408 | my %seen; |
409 | |
410 | push @{$EXPORT_TAGS{all}}, |
411 | grep {!$seen{$_}++} @{$EXPORT_TAGS{$_}} |
412 | foreach qw/html2 html3 netscape form cgi internal/; |
413 | } |
414 | |
3e927c50 |
415 | Note that the tag names in C<%EXPORT_TAGS> don't have the leading ':'. |
d584343b |
416 | |
5fea0f12 |
417 | =head2 C<AUTOLOAD>ed Constants |
418 | |
8b4c0206 |
419 | Many modules make use of C<AUTOLOAD>ing for constant subroutines to |
420 | avoid having to compile and waste memory on rarely used values (see |
421 | L<perlsub> for details on constant subroutines). Calls to such |
422 | constant subroutines are not optimized away at compile time because |
423 | they can't be checked at compile time for constancy. |
424 | |
425 | Even if a prototype is available at compile time, the body of the |
426 | subroutine is not (it hasn't been C<AUTOLOAD>ed yet). perl needs to |
427 | examine both the C<()> prototype and the body of a subroutine at |
428 | compile time to detect that it can safely replace calls to that |
429 | subroutine with the constant value. |
5fea0f12 |
430 | |
431 | A workaround for this is to call the constants once in a C<BEGIN> block: |
432 | |
433 | package My ; |
434 | |
435 | use Socket ; |
436 | |
437 | foo( SO_LINGER ); ## SO_LINGER NOT optimized away; called at runtime |
438 | BEGIN { SO_LINGER } |
439 | foo( SO_LINGER ); ## SO_LINGER optimized away at compile time. |
440 | |
8b4c0206 |
441 | This forces the C<AUTOLOAD> for C<SO_LINGER> to take place before |
442 | SO_LINGER is encountered later in C<My> package. |
5fea0f12 |
443 | |
8b4c0206 |
444 | If you are writing a package that C<AUTOLOAD>s, consider forcing |
445 | an C<AUTOLOAD> for any constants explicitly imported by other packages |
446 | or which are usually used when your package is C<use>d. |
5fea0f12 |
447 | |
47f97feb |
448 | =head1 Good Practices |
449 | |
450 | =head2 Declaring C<@EXPORT_OK> and Friends |
451 | |
452 | When using C<Exporter> with the standard C<strict> and C<warnings> |
453 | pragmas, the C<our> keyword is needed to declare the package |
454 | variables C<@EXPORT_OK>, C<@EXPORT>, C<@ISA>, etc. |
455 | |
456 | our @ISA = qw(Exporter); |
457 | our @EXPORT_OK = qw(munge frobnicate); |
458 | |
459 | If backward compatibility for Perls under 5.6 is important, |
460 | one must write instead a C<use vars> statement. |
461 | |
462 | use vars qw(@ISA @EXPORT_OK); |
463 | @ISA = qw(Exporter); |
464 | @EXPORT_OK = qw(munge frobnicate); |
465 | |
466 | =head2 Playing Safe |
467 | |
468 | There are some caveats with the use of runtime statements |
469 | like C<require Exporter> and the assignment to package |
470 | variables, which can very subtle for the unaware programmer. |
471 | This may happen for instance with mutually recursive |
472 | modules, which are affected by the time the relevant |
473 | constructions are executed. |
474 | |
475 | The ideal (but a bit ugly) way to never have to think |
476 | about that is to use C<BEGIN> blocks. So the first part |
477 | of the L</SYNOPSIS> code could be rewritten as: |
478 | |
479 | package YourModule; |
480 | |
481 | use strict; |
482 | use warnings; |
483 | |
484 | our (@ISA, @EXPORT_OK); |
485 | BEGIN { |
486 | require Exporter; |
487 | @ISA = qw(Exporter); |
488 | @EXPORT_OK = qw(munge frobnicate); # symbols to export on request |
489 | } |
490 | |
491 | The C<BEGIN> will assure that the loading of F<Exporter.pm> |
492 | and the assignments to C<@ISA> and C<@EXPORT_OK> happen |
493 | immediately, leaving no room for something to get awry |
494 | or just plain wrong. |
495 | |
496 | With respect to loading C<Exporter> and inheriting, there |
497 | are alternatives with the use of modules like C<base> and C<parent>. |
498 | |
499 | use base qw( Exporter ); |
500 | # or |
501 | use parent qw( Exporter ); |
502 | |
503 | Any of these statements are nice replacements for |
504 | C<BEGIN { require Exporter; @ISA = qw(Exporter); }> |
505 | with the same compile-time effect. The basic difference |
506 | is that C<base> code interacts with declared C<fields> |
507 | while C<parent> is a streamlined version of the older |
508 | C<base> code to just establish the IS-A relationship. |
509 | |
510 | For more details, see the documentation and code of |
511 | L<base> and L<parent>. |
512 | |
af30f7a9 |
513 | Another thorough remedy to that runtime vs. |
514 | compile-time trap is to use L<Exporter::Easy>, |
515 | which is a wrapper of Exporter that allows all |
516 | boilerplate code at a single gulp in the |
517 | use statement. |
518 | |
519 | use Exporter::Easy ( |
520 | OK => [ qw(munge frobnicate) ], |
521 | ); |
522 | # @ISA setup is automatic |
523 | # all assignments happen at compile time |
524 | |
47f97feb |
525 | =head2 What not to Export |
526 | |
af30f7a9 |
527 | You have been warned already in L</Selecting What To Export> |
47f97feb |
528 | to not export: |
529 | |
530 | =over 4 |
531 | |
532 | =item * |
533 | |
44ddc072 |
534 | method names (because you don't need to |
47f97feb |
535 | and that's likely to not do what you want), |
536 | |
537 | =item * |
538 | |
539 | anything by default (because you don't want to surprise your users... |
540 | badly) |
541 | |
542 | =item * |
543 | |
544 | anything you don't need to (because less is more) |
545 | |
546 | =back |
547 | |
548 | There's one more item to add to this list. Do B<not> |
549 | export variable names. Just because C<Exporter> lets you |
550 | do that, it does not mean you should. |
551 | |
552 | @EXPORT_OK = qw( $svar @avar %hvar ); # DON'T! |
553 | |
554 | Exporting variables is not a good idea. They can |
555 | change under the hood, provoking horrible |
556 | effects at-a-distance, that are too hard to track |
557 | and to fix. Trust me: they are not worth it. |
558 | |
559 | To provide the capability to set/get class-wide |
560 | settings, it is best instead to provide accessors |
561 | as subroutines or class methods instead. |
562 | |
563 | =head1 SEE ALSO |
564 | |
565 | C<Exporter> is definitely not the only module with |
566 | symbol exporter capabilities. At CPAN, you may find |
567 | a bunch of them. Some are lighter. Some |
568 | provide improved APIs and features. Peek the one |
569 | that fits your needs. The following is |
570 | a sample list of such modules. |
571 | |
572 | Exporter::Easy |
573 | Exporter::Lite |
574 | Exporter::Renaming |
575 | Exporter::Tidy |
576 | Sub::Exporter / Sub::Installer |
577 | Perl6::Export / Perl6::Export::Attrs |
578 | |
579 | =head1 LICENSE |
580 | |
581 | This library is free software. You can redistribute it |
582 | and/or modify it under the same terms as Perl itself. |
583 | |
2b5b2650 |
584 | =cut |
3e927c50 |
585 | |
586 | |
587 | |