6 $Verbose = 0 unless $Verbose;
12 # First make import warnings look like they're coming from the "use".
13 local $SIG{__WARN__} = sub {
15 $text =~ s/ at \S*Exporter.pm line \d+.*\n//;
16 local $Carp::CarpLevel = 1; # ignore package calling us too.
19 local $SIG{__DIE__} = sub {
20 Carp::croak("$_[0]Illegal null symbol in \@${1}::EXPORT")
21 if $_[0] =~ /^Unable to create sub named "(.*?)::"/;
24 my($pkg, $callpkg, @imports) = @_;
25 my($type, $sym, $oops);
26 *exports = *{"${pkg}::EXPORT"};
30 grep(s/^&//, @exports);
31 @exports{@exports} = (1) x @exports;
32 my $ok = \@{"${pkg}::EXPORT_OK"};
35 @exports{@$ok} = (1) x @$ok;
39 if ($imports[0] =~ m#^[/!:]#){
40 my $tagsref = \%{"${pkg}::EXPORT_TAGS"};
43 my($remove, $spec, @names, @allexports);
44 # negated first item implies starting with default set:
45 unshift @imports, ':DEFAULT' if $imports[0] =~ m/^!/;
46 foreach $spec (@imports){
47 $remove = $spec =~ s/^!//;
50 if ($spec eq 'DEFAULT'){
53 elsif ($tagdata = $tagsref->{$spec}) {
57 warn qq["$spec" is not defined in %${pkg}::EXPORT_TAGS];
62 elsif ($spec =~ m:^/(.*)/$:){
64 @allexports = keys %exports unless @allexports; # only do keys once
65 @names = grep(/$patn/, @allexports); # not anchored by default
68 @names = ($spec); # is a normal symbol name
71 warn "Import ".($remove ? "del":"add").": @names "
75 foreach $sym (@names) { delete $imports{$sym} }
78 @imports{@names} = (1) x @names;
81 @imports = keys %imports;
84 foreach $sym (@imports) {
85 if (!$exports{$sym}) {
87 $pkg->require_version($sym);
88 # If the version number was the only thing specified
89 # then we should act as if nothing was specified:
94 # We need a way to emulate 'use Foo ()' but still
95 # allow an easy version check: "use Foo 1.23, ''";
96 if (@imports == 2 and !$imports[1]) {
100 } elsif ($sym !~ s/^&// || !$exports{$sym}) {
101 warn qq["$sym" is not exported by the $pkg module];
106 Carp::croak("Can't continue after import errors") if $oops;
112 *fail = *{"${pkg}::EXPORT_FAIL"};
115 # Build cache of symbols. Optimise the lookup by adding
116 # barewords twice... both with and without a leading &.
117 # (Technique could be applied to %exports cache at cost of memory)
118 my @expanded = map { /^\w/ ? ($_, '&'.$_) : $_ } @fail;
119 warn "${pkg}::EXPORT_FAIL cached: @expanded" if $Verbose;
120 @fail{@expanded} = (1) x @expanded;
123 foreach $sym (@imports) { push(@failed, $sym) if $fail{$sym} }
125 @failed = $pkg->export_fail(@failed);
126 foreach $sym (@failed) {
127 warn qq["$sym" is not implemented by the $pkg module ],
128 "on this architecture";
130 Carp::croak("Can't continue after import errors") if @failed;
134 warn "Importing into $callpkg from $pkg: ",
135 join(", ",sort @imports) if $Verbose;
137 foreach $sym (@imports) {
138 # shortcut for the common case of no type character
139 (*{"${callpkg}::$sym"} = \&{"${pkg}::$sym"}, next)
140 unless $sym =~ s/^(\W)//;
142 *{"${callpkg}::$sym"} =
143 $type eq '&' ? \&{"${pkg}::$sym"} :
144 $type eq '$' ? \${"${pkg}::$sym"} :
145 $type eq '@' ? \@{"${pkg}::$sym"} :
146 $type eq '%' ? \%{"${pkg}::$sym"} :
147 $type eq '*' ? *{"${pkg}::$sym"} :
148 Carp::croak("Can't export symbol: $type$sym");
154 my $callpkg = caller($ExportLevel);
155 export $pkg, $callpkg, @_;
162 my($pkg, $var, $syms) = @_;
164 *export_tags = \%{"${pkg}::EXPORT_TAGS"};
165 push(@{"${pkg}::$var"},
166 map { $export_tags{$_} ? @{$export_tags{$_}} : scalar(++$nontag,$_) }
167 (@$syms) ? @$syms : keys %export_tags);
168 # This may change to a die one day
169 Carp::carp("Some names are not tags") if $nontag and $^W;
172 sub export_tags { _push_tags((caller)[0], "EXPORT", \@_) }
173 sub export_ok_tags { _push_tags((caller)[0], "EXPORT_OK", \@_) }
183 sub require_version {
184 my($self, $wanted) = @_;
185 my $pkg = ref $self || $self;
186 my $version = ${"${pkg}::VERSION"};
187 if (!$version or $version < $wanted) {
188 $version ||= "(undef)";
189 my $file = $INC{"$pkg.pm"};
190 $file &&= " ($file)";
191 Carp::croak("$pkg $wanted required--this is only version $version$file")
198 # A simple self test harness. Change 'require Carp' to 'use Carp ()' for testing.
199 # package main; eval(join('',<DATA>)) or die $@ unless caller;
202 $INC{'Exporter.pm'} = 1;
204 @EXPORT = qw(A1 A2 A3 A4 A5);
205 @EXPORT_OK = qw(B1 B2 B3 B4 B5);
206 %EXPORT_TAGS = (T1=>[qw(A1 A2 B1 B2)], T2=>[qw(A1 A2 B3 B4)], T3=>[qw(X3)]);
207 @EXPORT_FAIL = qw(B4);
208 Exporter::export_ok_tags('T3', 'unknown_tag');
210 map { "Test::$_" } @_ # edit symbols just as an example
214 $Exporter::Verbose = 1;
216 #import Test qw(X3); # export ok via export_ok_tags()
217 #import Test qw(:T1 !A2 /5/ !/3/ B5);
218 import Test qw(:T2 !B4);
219 import Test qw(:T2); # should fail
224 Exporter - Implements default import method for modules
228 In module ModuleName.pm:
234 @EXPORT = qw(...); # symbols to export by default
235 @EXPORT_OK = qw(...); # symbols to export on request
236 %EXPORT_TAGS = tag => [...]; # define names for sets of symbols
238 In other files which wish to use ModuleName:
240 use ModuleName; # import default symbols into my package
242 use ModuleName qw(...); # import listed symbols into my package
244 use ModuleName (); # do not import any symbols
248 The Exporter module implements a default C<import> method which
249 many modules choose inherit rather than implement their own.
251 Perl automatically calls the C<import> method when processing a
252 C<use> statement for a module. Modules and C<use> are documented
253 in L<perlfunc> and L<perlmod>. Understanding the concept of
254 modules and how the C<use> statement operates is important to
255 understanding the Exporter.
257 =head2 Selecting What To Export
259 Do B<not> export method names!
261 Do B<not> export anything else by default without a good reason!
263 Exports pollute the namespace of the module user. If you must export
264 try to use @EXPORT_OK in preference to @EXPORT and avoid short or
265 common symbol names to reduce the risk of name clashes.
267 Generally anything not exported is still accessible from outside the
268 module using the ModuleName::item_name (or $blessed_ref-E<gt>method)
269 syntax. By convention you can use a leading underscore on names to
270 informally indicate that they are 'internal' and not for public use.
272 (It is actually possible to get private functions by saying:
274 my $subref = sub { ... };
277 But there's no way to call that directly as a method, since a method
278 must have a name in the symbol table.)
280 As a general rule, if the module is trying to be object oriented
281 then export nothing. If it's just a collection of functions then
282 @EXPORT_OK anything but use @EXPORT with caution.
284 Other module design guidelines can be found in L<perlmod>.
286 =head2 Specialised Import Lists
288 If the first entry in an import list begins with !, : or / then the
289 list is treated as a series of specifications which either add to or
290 delete from the list of names to import. They are processed left to
291 right. Specifications are in the form:
293 [!]name This name only
294 [!]:DEFAULT All names in @EXPORT
295 [!]:tag All names in $EXPORT_TAGS{tag} anonymous list
296 [!]/pattern/ All names in @EXPORT and @EXPORT_OK which match
298 A leading ! indicates that matching names should be deleted from the
299 list of names to import. If the first specification is a deletion it
300 is treated as though preceded by :DEFAULT. If you just want to import
301 extra names in addition to the default set you will still need to
302 include :DEFAULT explicitly.
304 e.g., Module.pm defines:
306 @EXPORT = qw(A1 A2 A3 A4 A5);
307 @EXPORT_OK = qw(B1 B2 B3 B4 B5);
308 %EXPORT_TAGS = (T1 => [qw(A1 A2 B1 B2)], T2 => [qw(A1 A2 B3 B4)]);
310 Note that you cannot use tags in @EXPORT or @EXPORT_OK.
311 Names in EXPORT_TAGS must also appear in @EXPORT or @EXPORT_OK.
313 An application using Module can say something like:
315 use Module qw(:DEFAULT :T2 !B3 A3);
317 Other examples include:
319 use Socket qw(!/^[AP]F_/ !SOMAXCONN !SOL_SOCKET);
320 use POSIX qw(:errno_h :termios_h !TCSADRAIN !/^EXIT/);
322 Remember that most patterns (using //) will need to be anchored
323 with a leading ^, e.g., C</^EXIT/> rather than C</EXIT/>.
325 You can say C<BEGIN { $Exporter::Verbose=1 }> to see how the
326 specifications are being processed and what is actually being imported
329 =head2 Module Version Checking
331 The Exporter module will convert an attempt to import a number from a
332 module into a call to $module_name-E<gt>require_version($value). This can
333 be used to validate that the version of the module being used is
334 greater than or equal to the required version.
336 The Exporter module supplies a default require_version method which
337 checks the value of $VERSION in the exporting module.
339 Since the default require_version method treats the $VERSION number as
340 a simple numeric value it will regard version 1.10 as lower than
341 1.9. For this reason it is strongly recommended that you use numbers
342 with at least two decimal places, e.g., 1.09.
344 =head2 Managing Unknown Symbols
346 In some situations you may want to prevent certain symbols from being
347 exported. Typically this applies to extensions which have functions
348 or constants that may not exist on some systems.
350 The names of any symbols that cannot be exported should be listed
351 in the C<@EXPORT_FAIL> array.
353 If a module attempts to import any of these symbols the Exporter will
354 will give the module an opportunity to handle the situation before
355 generating an error. The Exporter will call an export_fail method
356 with a list of the failed symbols:
358 @failed_symbols = $module_name->export_fail(@failed_symbols);
360 If the export_fail method returns an empty list then no error is
361 recorded and all the requested symbols are exported. If the returned
362 list is not empty then an error is generated for each symbol and the
363 export fails. The Exporter provides a default export_fail method which
364 simply returns the list unchanged.
366 Uses for the export_fail method include giving better error messages
367 for some symbols and performing lazy architectural checks (put more
368 symbols into @EXPORT_FAIL by default and then take them out if someone
369 actually tries to use them and an expensive check shows that they are
370 usable on that platform).
372 =head2 Tag Handling Utility Functions
374 Since the symbols listed within %EXPORT_TAGS must also appear in either
375 @EXPORT or @EXPORT_OK, two utility functions are provided which allow
376 you to easily add tagged sets of symbols to @EXPORT or @EXPORT_OK:
378 %EXPORT_TAGS = (foo => [qw(aa bb cc)], bar => [qw(aa cc dd)]);
380 Exporter::export_tags('foo'); # add aa, bb and cc to @EXPORT
381 Exporter::export_ok_tags('bar'); # add aa, cc and dd to @EXPORT_OK
383 Any names which are not tags are added to @EXPORT or @EXPORT_OK
384 unchanged but will trigger a warning (with C<-w>) to avoid misspelt tags
385 names being silently added to @EXPORT or @EXPORT_OK. Future versions
386 may make this a fatal error.