10 require Exporter::Heavy;
11 goto &heavy_export_to_level;
15 require Exporter::Heavy;
20 require Exporter::Heavy;
21 _push_tags((caller)[0], "EXPORT", \@_);
25 require Exporter::Heavy;
26 _push_tags((caller)[0], "EXPORT_OK", \@_);
31 my $callpkg = caller($ExportLevel);
32 *exports = *{"$pkg\::EXPORT"};
33 # We *need* to treat @{"$pkg\::EXPORT_FAIL"} since Carp uses it :-(
34 *fail = *{"$pkg\::EXPORT_FAIL"};
35 return export $pkg, $callpkg, @_
36 if $Verbose or $Debug or @fail > 1;
37 my $args = @_ or @_ = @exports;
39 if ($args and not %exports) {
40 foreach my $sym (@exports, @{"$pkg\::EXPORT_OK"}) {
46 #need to match first to avoid "Modification of a read-only value attempted"
47 if (/^\+/ and s/^\+//) {
48 (\&{"$pkg\::$_"})->(); #try AUTOLOAD now so calls are inlined
51 if ($Verbose or $Debug
52 or grep {/\W/ or $args and not exists $exports{$_}
53 or @fail and $_ eq $fail[0]
54 or (@{"$pkg\::EXPORT_OK"}
55 and $_ eq ${"$pkg\::EXPORT_OK"}[0])} @_) {
56 return export $pkg, $callpkg, ($args ? @_ : ());
58 #local $SIG{__WARN__} = sub {require Carp; goto &Carp::carp};
59 local $SIG{__WARN__} =
60 sub {require Carp; local $Carp::CarpLevel = 1; &Carp::carp};
62 # shortcut for the common case of no type character
63 *{"$callpkg\::$sym"} = \&{"$pkg\::$sym"};
69 # A simple self test harness. Change 'require Carp' to 'use Carp ()' for testing.
70 # package main; eval(join('',<DATA>)) or die $@ unless caller;
73 $INC{'Exporter.pm'} = 1;
75 @EXPORT = qw(A1 A2 A3 A4 A5);
76 @EXPORT_OK = qw(B1 B2 B3 B4 B5);
77 %EXPORT_TAGS = (T1=>[qw(A1 A2 B1 B2)], T2=>[qw(A1 A2 B3 B4)], T3=>[qw(X3)]);
78 @EXPORT_FAIL = qw(B4);
79 Exporter::export_ok_tags('T3', 'unknown_tag');
81 map { "Test::$_" } @_ # edit symbols just as an example
85 $Exporter::Verbose = 1;
87 #import Test qw(X3); # export ok via export_ok_tags()
88 #import Test qw(:T1 !A2 /5/ !/3/ B5);
89 import Test qw(:T2 !B4);
90 import Test qw(:T2); # should fail
95 Exporter - Implements default import method for modules
99 In module ModuleName.pm:
105 @EXPORT = qw(...); # symbols to export by default
106 @EXPORT_OK = qw(...); # symbols to export on request
107 %EXPORT_TAGS = tag => [...]; # define names for sets of symbols
109 In other files which wish to use ModuleName:
111 use ModuleName; # import default symbols into my package
113 use ModuleName qw(...); # import listed symbols into my package
115 use ModuleName (); # do not import any symbols
119 The Exporter module implements a default C<import> method which
120 many modules choose to inherit rather than implement their own.
122 Perl automatically calls the C<import> method when processing a
123 C<use> statement for a module. Modules and C<use> are documented
124 in L<perlfunc> and L<perlmod>. Understanding the concept of
125 modules and how the C<use> statement operates is important to
126 understanding the Exporter.
130 The arrays C<@EXPORT> and C<@EXPORT_OK> in a module hold lists of
131 symbols that are going to be exported into the users name space by
132 default, or which they can request to be exported, respectively. The
133 symbols can represent functions, scalars, arrays, hashes, or typeglobs.
134 The symbols must be given by full name with the exception that the
135 ampersand in front of a function is optional, e.g.
137 @EXPORT = qw(afunc $scalar @array); # afunc is a function
138 @EXPORT_OK = qw(&bfunc %hash *typeglob); # explicit prefix on &bfunc
140 =head2 Selecting What To Export
142 Do B<not> export method names!
144 Do B<not> export anything else by default without a good reason!
146 Exports pollute the namespace of the module user. If you must export
147 try to use @EXPORT_OK in preference to @EXPORT and avoid short or
148 common symbol names to reduce the risk of name clashes.
150 Generally anything not exported is still accessible from outside the
151 module using the ModuleName::item_name (or $blessed_ref-E<gt>method)
152 syntax. By convention you can use a leading underscore on names to
153 informally indicate that they are 'internal' and not for public use.
155 (It is actually possible to get private functions by saying:
157 my $subref = sub { ... };
160 But there's no way to call that directly as a method, since a method
161 must have a name in the symbol table.)
163 As a general rule, if the module is trying to be object oriented
164 then export nothing. If it's just a collection of functions then
165 @EXPORT_OK anything but use @EXPORT with caution.
167 Other module design guidelines can be found in L<perlmod>.
169 =head2 Specialised Import Lists
171 If the first entry in an import list begins with !, : or / then the
172 list is treated as a series of specifications which either add to or
173 delete from the list of names to import. They are processed left to
174 right. Specifications are in the form:
176 [!]name This name only
177 [!]:DEFAULT All names in @EXPORT
178 [!]:tag All names in $EXPORT_TAGS{tag} anonymous list
179 [!]/pattern/ All names in @EXPORT and @EXPORT_OK which match
181 A leading ! indicates that matching names should be deleted from the
182 list of names to import. If the first specification is a deletion it
183 is treated as though preceded by :DEFAULT. If you just want to import
184 extra names in addition to the default set you will still need to
185 include :DEFAULT explicitly.
187 e.g., Module.pm defines:
189 @EXPORT = qw(A1 A2 A3 A4 A5);
190 @EXPORT_OK = qw(B1 B2 B3 B4 B5);
191 %EXPORT_TAGS = (T1 => [qw(A1 A2 B1 B2)], T2 => [qw(A1 A2 B3 B4)]);
193 Note that you cannot use tags in @EXPORT or @EXPORT_OK.
194 Names in EXPORT_TAGS must also appear in @EXPORT or @EXPORT_OK.
196 An application using Module can say something like:
198 use Module qw(:DEFAULT :T2 !B3 A3);
200 Other examples include:
202 use Socket qw(!/^[AP]F_/ !SOMAXCONN !SOL_SOCKET);
203 use POSIX qw(:errno_h :termios_h !TCSADRAIN !/^EXIT/);
205 Remember that most patterns (using //) will need to be anchored
206 with a leading ^, e.g., C</^EXIT/> rather than C</EXIT/>.
208 You can say C<BEGIN { $Exporter::Verbose=1 }> to see how the
209 specifications are being processed and what is actually being imported
212 =head2 Exporting without using Export's import method
214 Exporter has a special method, 'export_to_level' which is used in situations
215 where you can't directly call Export's import method. The export_to_level
218 MyPackage->export_to_level($where_to_export, $package, @what_to_export);
220 where $where_to_export is an integer telling how far up the calling stack
221 to export your symbols, and @what_to_export is an array telling what
222 symbols *to* export (usually this is @_). The $package argument is
225 For example, suppose that you have a module, A, which already has an
231 @EXPORT_OK = qw ($b);
235 $A::b = 1; # not a very useful import method
238 and you want to Export symbol $A::b back to the module that called
239 package A. Since Exporter relies on the import method to work, via
240 inheritance, as it stands Exporter::import() will never get called.
241 Instead, say the following:
245 @EXPORT_OK = qw ($b);
250 A->export_to_level(1, @_);
253 This will export the symbols one level 'above' the current package - ie: to
254 the program or module that used package A.
256 Note: Be careful not to modify '@_' at all before you call export_to_level
257 - or people using your package will get very unexplained results!
260 =head2 Module Version Checking
262 The Exporter module will convert an attempt to import a number from a
263 module into a call to $module_name-E<gt>require_version($value). This can
264 be used to validate that the version of the module being used is
265 greater than or equal to the required version.
267 The Exporter module supplies a default require_version method which
268 checks the value of $VERSION in the exporting module.
270 Since the default require_version method treats the $VERSION number as
271 a simple numeric value it will regard version 1.10 as lower than
272 1.9. For this reason it is strongly recommended that you use numbers
273 with at least two decimal places, e.g., 1.09.
275 =head2 Managing Unknown Symbols
277 In some situations you may want to prevent certain symbols from being
278 exported. Typically this applies to extensions which have functions
279 or constants that may not exist on some systems.
281 The names of any symbols that cannot be exported should be listed
282 in the C<@EXPORT_FAIL> array.
284 If a module attempts to import any of these symbols the Exporter
285 will give the module an opportunity to handle the situation before
286 generating an error. The Exporter will call an export_fail method
287 with a list of the failed symbols:
289 @failed_symbols = $module_name->export_fail(@failed_symbols);
291 If the export_fail method returns an empty list then no error is
292 recorded and all the requested symbols are exported. If the returned
293 list is not empty then an error is generated for each symbol and the
294 export fails. The Exporter provides a default export_fail method which
295 simply returns the list unchanged.
297 Uses for the export_fail method include giving better error messages
298 for some symbols and performing lazy architectural checks (put more
299 symbols into @EXPORT_FAIL by default and then take them out if someone
300 actually tries to use them and an expensive check shows that they are
301 usable on that platform).
303 =head2 Tag Handling Utility Functions
305 Since the symbols listed within %EXPORT_TAGS must also appear in either
306 @EXPORT or @EXPORT_OK, two utility functions are provided which allow
307 you to easily add tagged sets of symbols to @EXPORT or @EXPORT_OK:
309 %EXPORT_TAGS = (foo => [qw(aa bb cc)], bar => [qw(aa cc dd)]);
311 Exporter::export_tags('foo'); # add aa, bb and cc to @EXPORT
312 Exporter::export_ok_tags('bar'); # add aa, cc and dd to @EXPORT_OK
314 Any names which are not tags are added to @EXPORT or @EXPORT_OK
315 unchanged but will trigger a warning (with C<-w>) to avoid misspelt tags
316 names being silently added to @EXPORT or @EXPORT_OK. Future versions
317 may make this a fatal error.