9 require Exporter::Heavy;
10 goto &heavy_export_to_level;
14 require Exporter::Heavy;
19 require Exporter::Heavy;
20 _push_tags((caller)[0], "EXPORT", \@_);
24 require Exporter::Heavy;
25 _push_tags((caller)[0], "EXPORT_OK", \@_);
30 my $callpkg = caller($ExportLevel);
31 *exports = *{"$pkg\::EXPORT"};
32 # We *need* to treat @{"$pkg\::EXPORT_FAIL"} since Carp uses it :-(
33 *fail = *{"$pkg\::EXPORT_FAIL"};
34 return export $pkg, $callpkg, @_
35 if $Verbose or $Debug or @fail > 1;
36 my $args = @_ or @_ = @exports;
38 if ($args and not %exports) {
39 foreach my $sym (@exports, @{"$pkg\::EXPORT_OK"}) {
44 if ($Verbose or $Debug
45 or grep {/\W/ or $args and not exists $exports{$_}
46 or @fail and $_ eq $fail[0]
47 or (@{"$pkg\::EXPORT_OK"}
48 and $_ eq ${"$pkg\::EXPORT_OK"}[0])} @_) {
49 return export $pkg, $callpkg, ($args ? @_ : ());
51 #local $SIG{__WARN__} = sub {require Carp; goto &Carp::carp};
52 local $SIG{__WARN__} =
53 sub {require Carp; local $Carp::CarpLevel = 1; &Carp::carp};
55 # shortcut for the common case of no type character
56 *{"$callpkg\::$sym"} = \&{"$pkg\::$sym"};
62 # A simple self test harness. Change 'require Carp' to 'use Carp ()' for testing.
63 # package main; eval(join('',<DATA>)) or die $@ unless caller;
66 $INC{'Exporter.pm'} = 1;
68 @EXPORT = qw(A1 A2 A3 A4 A5);
69 @EXPORT_OK = qw(B1 B2 B3 B4 B5);
70 %EXPORT_TAGS = (T1=>[qw(A1 A2 B1 B2)], T2=>[qw(A1 A2 B3 B4)], T3=>[qw(X3)]);
71 @EXPORT_FAIL = qw(B4);
72 Exporter::export_ok_tags('T3', 'unknown_tag');
74 map { "Test::$_" } @_ # edit symbols just as an example
78 $Exporter::Verbose = 1;
80 #import Test qw(X3); # export ok via export_ok_tags()
81 #import Test qw(:T1 !A2 /5/ !/3/ B5);
82 import Test qw(:T2 !B4);
83 import Test qw(:T2); # should fail
88 Exporter - Implements default import method for modules
92 In module ModuleName.pm:
98 @EXPORT = qw(...); # symbols to export by default
99 @EXPORT_OK = qw(...); # symbols to export on request
100 %EXPORT_TAGS = tag => [...]; # define names for sets of symbols
102 In other files which wish to use ModuleName:
104 use ModuleName; # import default symbols into my package
106 use ModuleName qw(...); # import listed symbols into my package
108 use ModuleName (); # do not import any symbols
112 The Exporter module implements a default C<import> method which
113 many modules choose to inherit rather than implement their own.
115 Perl automatically calls the C<import> method when processing a
116 C<use> statement for a module. Modules and C<use> are documented
117 in L<perlfunc> and L<perlmod>. Understanding the concept of
118 modules and how the C<use> statement operates is important to
119 understanding the Exporter.
121 =head2 Selecting What To Export
123 Do B<not> export method names!
125 Do B<not> export anything else by default without a good reason!
127 Exports pollute the namespace of the module user. If you must export
128 try to use @EXPORT_OK in preference to @EXPORT and avoid short or
129 common symbol names to reduce the risk of name clashes.
131 Generally anything not exported is still accessible from outside the
132 module using the ModuleName::item_name (or $blessed_ref-E<gt>method)
133 syntax. By convention you can use a leading underscore on names to
134 informally indicate that they are 'internal' and not for public use.
136 (It is actually possible to get private functions by saying:
138 my $subref = sub { ... };
141 But there's no way to call that directly as a method, since a method
142 must have a name in the symbol table.)
144 As a general rule, if the module is trying to be object oriented
145 then export nothing. If it's just a collection of functions then
146 @EXPORT_OK anything but use @EXPORT with caution.
148 Other module design guidelines can be found in L<perlmod>.
150 =head2 Specialised Import Lists
152 If the first entry in an import list begins with !, : or / then the
153 list is treated as a series of specifications which either add to or
154 delete from the list of names to import. They are processed left to
155 right. Specifications are in the form:
157 [!]name This name only
158 [!]:DEFAULT All names in @EXPORT
159 [!]:tag All names in $EXPORT_TAGS{tag} anonymous list
160 [!]/pattern/ All names in @EXPORT and @EXPORT_OK which match
162 A leading ! indicates that matching names should be deleted from the
163 list of names to import. If the first specification is a deletion it
164 is treated as though preceded by :DEFAULT. If you just want to import
165 extra names in addition to the default set you will still need to
166 include :DEFAULT explicitly.
168 e.g., Module.pm defines:
170 @EXPORT = qw(A1 A2 A3 A4 A5);
171 @EXPORT_OK = qw(B1 B2 B3 B4 B5);
172 %EXPORT_TAGS = (T1 => [qw(A1 A2 B1 B2)], T2 => [qw(A1 A2 B3 B4)]);
174 Note that you cannot use tags in @EXPORT or @EXPORT_OK.
175 Names in EXPORT_TAGS must also appear in @EXPORT or @EXPORT_OK.
177 An application using Module can say something like:
179 use Module qw(:DEFAULT :T2 !B3 A3);
181 Other examples include:
183 use Socket qw(!/^[AP]F_/ !SOMAXCONN !SOL_SOCKET);
184 use POSIX qw(:errno_h :termios_h !TCSADRAIN !/^EXIT/);
186 Remember that most patterns (using //) will need to be anchored
187 with a leading ^, e.g., C</^EXIT/> rather than C</EXIT/>.
189 You can say C<BEGIN { $Exporter::Verbose=1 }> to see how the
190 specifications are being processed and what is actually being imported
193 =head2 Exporting without using Export's import method
195 Exporter has a special method, 'export_to_level' which is used in situations
196 where you can't directly call Export's import method. The export_to_level
199 MyPackage->export_to_level($where_to_export, $package, @what_to_export);
201 where $where_to_export is an integer telling how far up the calling stack
202 to export your symbols, and @what_to_export is an array telling what
203 symbols *to* export (usually this is @_). The $package argument is
206 For example, suppose that you have a module, A, which already has an
212 @EXPORT_OK = qw ($b);
216 $A::b = 1; # not a very useful import method
219 and you want to Export symbol $A::b back to the module that called
220 package A. Since Exporter relies on the import method to work, via
221 inheritance, as it stands Exporter::import() will never get called.
222 Instead, say the following:
226 @EXPORT_OK = qw ($b);
231 A->export_to_level(1, @_);
234 This will export the symbols one level 'above' the current package - ie: to
235 the program or module that used package A.
237 Note: Be careful not to modify '@_' at all before you call export_to_level
238 - or people using your package will get very unexplained results!
241 =head2 Module Version Checking
243 The Exporter module will convert an attempt to import a number from a
244 module into a call to $module_name-E<gt>require_version($value). This can
245 be used to validate that the version of the module being used is
246 greater than or equal to the required version.
248 The Exporter module supplies a default require_version method which
249 checks the value of $VERSION in the exporting module.
251 Since the default require_version method treats the $VERSION number as
252 a simple numeric value it will regard version 1.10 as lower than
253 1.9. For this reason it is strongly recommended that you use numbers
254 with at least two decimal places, e.g., 1.09.
256 =head2 Managing Unknown Symbols
258 In some situations you may want to prevent certain symbols from being
259 exported. Typically this applies to extensions which have functions
260 or constants that may not exist on some systems.
262 The names of any symbols that cannot be exported should be listed
263 in the C<@EXPORT_FAIL> array.
265 If a module attempts to import any of these symbols the Exporter
266 will give the module an opportunity to handle the situation before
267 generating an error. The Exporter will call an export_fail method
268 with a list of the failed symbols:
270 @failed_symbols = $module_name->export_fail(@failed_symbols);
272 If the export_fail method returns an empty list then no error is
273 recorded and all the requested symbols are exported. If the returned
274 list is not empty then an error is generated for each symbol and the
275 export fails. The Exporter provides a default export_fail method which
276 simply returns the list unchanged.
278 Uses for the export_fail method include giving better error messages
279 for some symbols and performing lazy architectural checks (put more
280 symbols into @EXPORT_FAIL by default and then take them out if someone
281 actually tries to use them and an expensive check shows that they are
282 usable on that platform).
284 =head2 Tag Handling Utility Functions
286 Since the symbols listed within %EXPORT_TAGS must also appear in either
287 @EXPORT or @EXPORT_OK, two utility functions are provided which allow
288 you to easily add tagged sets of symbols to @EXPORT or @EXPORT_OK:
290 %EXPORT_TAGS = (foo => [qw(aa bb cc)], bar => [qw(aa cc dd)]);
292 Exporter::export_tags('foo'); # add aa, bb and cc to @EXPORT
293 Exporter::export_ok_tags('bar'); # add aa, cc and dd to @EXPORT_OK
295 Any names which are not tags are added to @EXPORT or @EXPORT_OK
296 unchanged but will trigger a warning (with C<-w>) to avoid misspelt tags
297 names being silently added to @EXPORT or @EXPORT_OK. Future versions
298 may make this a fatal error.