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 { $Exporter::Verbose=1 }> to see how the
209 specifications are being processed and what is actually being imported
212 =head2 Constants can be inlined
214 AUTOLOADed constants can be inlined by prefixing them with a C<+>:
216 use Socket qw(+AF_INET);
218 Thusly prefixed constants are defined during the symbol import phase of
219 compilation, which means that by runtime they are true inlined constants.
221 =head2 Exporting without using Export's import method
223 Exporter has a special method, 'export_to_level' which is used in situations
224 where you can't directly call Export's import method. The export_to_level
227 MyPackage->export_to_level($where_to_export, $package, @what_to_export);
229 where $where_to_export is an integer telling how far up the calling stack
230 to export your symbols, and @what_to_export is an array telling what
231 symbols *to* export (usually this is @_). The $package argument is
234 For example, suppose that you have a module, A, which already has an
240 @EXPORT_OK = qw ($b);
244 $A::b = 1; # not a very useful import method
247 and you want to Export symbol $A::b back to the module that called
248 package A. Since Exporter relies on the import method to work, via
249 inheritance, as it stands Exporter::import() will never get called.
250 Instead, say the following:
254 @EXPORT_OK = qw ($b);
259 A->export_to_level(1, @_);
262 This will export the symbols one level 'above' the current package - ie: to
263 the program or module that used package A.
265 Note: Be careful not to modify '@_' at all before you call export_to_level
266 - or people using your package will get very unexplained results!
269 =head2 Module Version Checking
271 The Exporter module will convert an attempt to import a number from a
272 module into a call to $module_name-E<gt>require_version($value). This can
273 be used to validate that the version of the module being used is
274 greater than or equal to the required version.
276 The Exporter module supplies a default require_version method which
277 checks the value of $VERSION in the exporting module.
279 Since the default require_version method treats the $VERSION number as
280 a simple numeric value it will regard version 1.10 as lower than
281 1.9. For this reason it is strongly recommended that you use numbers
282 with at least two decimal places, e.g., 1.09.
284 =head2 Managing Unknown Symbols
286 In some situations you may want to prevent certain symbols from being
287 exported. Typically this applies to extensions which have functions
288 or constants that may not exist on some systems.
290 The names of any symbols that cannot be exported should be listed
291 in the C<@EXPORT_FAIL> array.
293 If a module attempts to import any of these symbols the Exporter
294 will give the module an opportunity to handle the situation before
295 generating an error. The Exporter will call an export_fail method
296 with a list of the failed symbols:
298 @failed_symbols = $module_name->export_fail(@failed_symbols);
300 If the export_fail method returns an empty list then no error is
301 recorded and all the requested symbols are exported. If the returned
302 list is not empty then an error is generated for each symbol and the
303 export fails. The Exporter provides a default export_fail method which
304 simply returns the list unchanged.
306 Uses for the export_fail method include giving better error messages
307 for some symbols and performing lazy architectural checks (put more
308 symbols into @EXPORT_FAIL by default and then take them out if someone
309 actually tries to use them and an expensive check shows that they are
310 usable on that platform).
312 =head2 Tag Handling Utility Functions
314 Since the symbols listed within %EXPORT_TAGS must also appear in either
315 @EXPORT or @EXPORT_OK, two utility functions are provided which allow
316 you to easily add tagged sets of symbols to @EXPORT or @EXPORT_OK:
318 %EXPORT_TAGS = (foo => [qw(aa bb cc)], bar => [qw(aa cc dd)]);
320 Exporter::export_tags('foo'); # add aa, bb and cc to @EXPORT
321 Exporter::export_ok_tags('bar'); # add aa, cc and dd to @EXPORT_OK
323 Any names which are not tags are added to @EXPORT or @EXPORT_OK
324 unchanged but will trigger a warning (with C<-w>) to avoid misspelt tags
325 names being silently added to @EXPORT or @EXPORT_OK. Future versions
326 may make this a fatal error.