X-Git-Url: http://git.shadowcat.co.uk/gitweb/gitweb.cgi?a=blobdiff_plain;f=lib%2FExporter.pm;h=8b8d4c49392bedc9c959ec99c0b3ad2ebb5d8138;hb=b11575486bfd20a8caa4a78b3ffbf747a1e95094;hp=bd55160f87741cd504ccdc2cf53face81bf98736;hpb=fa1bb02feecc6f4fdaff36b2895f96803af07c6a;p=p5sagit%2Fp5-mst-13.2.git diff --git a/lib/Exporter.pm b/lib/Exporter.pm index bd55160..8b8d4c4 100644 --- a/lib/Exporter.pm +++ b/lib/Exporter.pm @@ -2,33 +2,27 @@ package Exporter; require 5.006; -use strict; -no strict 'refs'; +# Be lean. +#use strict; +#no strict 'refs'; our $Debug = 0; our $ExportLevel = 0; our $Verbose ||= 0; -our $VERSION = '5.565'; +our $VERSION = '5.566'; $Carp::Internal{Exporter} = 1; -sub export_to_level { +sub as_heavy { require Exporter::Heavy; - goto &Exporter::Heavy::heavy_export_to_level; + # Unfortunately, this does not work if the caller is aliased as *name = \&foo + # Thus the need to create a lot of identical subroutines + my $c = (caller(1))[3]; + $c =~ s/.*:://; + \&{"Exporter::Heavy::heavy_$c"}; } sub export { - require Exporter::Heavy; - goto &Exporter::Heavy::heavy_export; -} - -sub export_tags { - require Exporter::Heavy; - Exporter::Heavy::_push_tags((caller)[0], "EXPORT", \@_); -} - -sub export_ok_tags { - require Exporter::Heavy; - Exporter::Heavy::_push_tags((caller)[0], "EXPORT_OK", \@_); + goto &{as_heavy()}; } sub import { @@ -65,7 +59,6 @@ sub import { *{"$callpkg\::$_"} = \&{"$pkg\::$_"} foreach @_; } - # Default methods sub export_fail { @@ -73,12 +66,25 @@ sub export_fail { @_; } +# Unfortunately, caller(1)[3] "does not work" if the caller is aliased as +# *name = \&foo. Thus the need to create a lot of identical subroutines +# Otherwise we could have aliased them to export(). -sub require_version { - require Exporter::Heavy; - goto &Exporter::Heavy::require_version; +sub export_to_level { + goto &{as_heavy()}; } +sub export_tags { + goto &{as_heavy()}; +} + +sub export_ok_tags { + goto &{as_heavy()}; +} + +sub require_version { + goto &{as_heavy()}; +} 1; __END__ @@ -89,28 +95,25 @@ Exporter - Implements default import method for modules =head1 SYNOPSIS -In module ModuleName.pm: +In module YourModule.pm: - package ModuleName; + package YourModule; require Exporter; @ISA = qw(Exporter); + @EXPORT_OK = qw(munge frobnicate); # symbols to export on request - @EXPORT = qw(...); # symbols to export by default - @EXPORT_OK = qw(...); # symbols to export on request - %EXPORT_TAGS = tag => [...]; # define names for sets of symbols - -In other files which wish to use ModuleName: - - use ModuleName; # import default symbols into my package +In other files which wish to use YourModule: - use ModuleName qw(...); # import listed symbols into my package - - use ModuleName (); # do not import any symbols + use ModuleName qw(frobnicate); # import listed symbols + frobnicate ($left, $right) # calls YourModule::frobnicate =head1 DESCRIPTION -The Exporter module implements a default C method which -many modules choose to inherit rather than implement their own. +The Exporter module implements an C method which allows a module +to export functions and variables to its users' namespaces. Many modules +use Exporter rather than implementing their own C method because +Exporter provides a highly flexible interface, with an implementation optimised +for the common case. Perl automatically calls the C method when processing a C statement for a module. Modules and C are documented @@ -130,6 +133,9 @@ ampersand in front of a function is optional, e.g. @EXPORT = qw(afunc $scalar @array); # afunc is a function @EXPORT_OK = qw(&bfunc %hash *typeglob); # explicit prefix on &bfunc +If you are only exporting function names it is recommended to omit the +ampersand, as the implementation is faster this way. + =head2 Selecting What To Export Do B export method names! @@ -156,10 +162,42 @@ how to make inheritance work.) As a general rule, if the module is trying to be object oriented then export nothing. If it's just a collection of functions then -@EXPORT_OK anything but use @EXPORT with caution. +@EXPORT_OK anything but use @EXPORT with caution. For function and +method names use barewords in preference to names prefixed with +ampersands for the export lists. Other module design guidelines can be found in L. +=head2 How to Import + +In other files which wish to use your module there are three basic ways for +them to load your module and import its symbols: + +=over 4 + +=item C + +This imports all the symbols from ModuleName's @EXPORT into the namespace +of the C statement. + +=item C + +This causes perl to load your module but does not import any symbols. + +=item C + +This imports only the symbols listed by the caller into their namespace. +All listed symbols must be in your @EXPORT or @EXPORT_OK, else an error +occurs. The advanced export features of Exporter are accessed like this, +but with list entries that are syntactically distinct from symbol names. + +=back + +Unless you want to use its advanced features, this is probably all you +need to know to use Exporter. + +=head1 Advanced features + =head2 Specialised Import Lists If the first entry in an import list begins with !, : or / then the @@ -203,13 +241,13 @@ You can say C to see how the specifications are being processed and what is actually being imported into modules. -=head2 Exporting without using Export's import method +=head2 Exporting without using Exporter's import method Exporter has a special method, 'export_to_level' which is used in situations -where you can't directly call Export's import method. The export_to_level +where you can't directly call Exporter's import method. The export_to_level method looks like: -MyPackage->export_to_level($where_to_export, $package, @what_to_export); + MyPackage->export_to_level($where_to_export, $package, @what_to_export); where $where_to_export is an integer telling how far up the calling stack to export your symbols, and @what_to_export is an array telling what @@ -219,30 +257,30 @@ currently unused. For example, suppose that you have a module, A, which already has an import function: -package A; + package A; -@ISA = qw(Exporter); -@EXPORT_OK = qw ($b); + @ISA = qw(Exporter); + @EXPORT_OK = qw ($b); -sub import -{ - $A::b = 1; # not a very useful import method -} + sub import + { + $A::b = 1; # not a very useful import method + } and you want to Export symbol $A::b back to the module that called package A. Since Exporter relies on the import method to work, via inheritance, as it stands Exporter::import() will never get called. Instead, say the following: -package A; -@ISA = qw(Exporter); -@EXPORT_OK = qw ($b); + package A; + @ISA = qw(Exporter); + @EXPORT_OK = qw ($b); -sub import -{ - $A::b = 1; - A->export_to_level(1, @_); -} + sub import + { + $A::b = 1; + A->export_to_level(1, @_); + } This will export the symbols one level 'above' the current package - ie: to the program or module that used package A. @@ -310,6 +348,40 @@ unchanged but will trigger a warning (with C<-w>) to avoid misspelt tags names being silently added to @EXPORT or @EXPORT_OK. Future versions may make this a fatal error. +=head2 Generating combined tags + +If several symbol categories exist in %EXPORT_TAGS, it's usually +useful to create the utility ":all" to simplify "use" statements. + +The simplest way to do this is: + + %EXPORT_TAGS = (foo => [qw(aa bb cc)], bar => [qw(aa cc dd)]); + + # add all the other ":class" tags to the ":all" class, + # deleting duplicates + { + my %seen; + + push @{$EXPORT_TAGS{all}}, + grep {!$seen{$_}++} @{$EXPORT_TAGS{$_}} foreach keys %EXPORT_TAGS; + } + +CGI.pm creates an ":all" tag which contains some (but not really +all) of its categories. That could be done with one small +change: + + # add some of the other ":class" tags to the ":all" class, + # deleting duplicates + { + my %seen; + + push @{$EXPORT_TAGS{all}}, + grep {!$seen{$_}++} @{$EXPORT_TAGS{$_}} + foreach qw/html2 html3 netscape form cgi internal/; + } + +Note that the tag names in %EXPORT_TAGS don't have the leading ':'. + =head2 Ced Constants Many modules make use of Cing for constant subroutines to