4 use warnings FATAL => 'all';
6 our $VERSION = '1.001001'; # 1.1.1
12 my ($package, $file, $line) = $target =~ /[^0-9]/ ? ($target) : caller($target + 1);
13 my $code = qq{package $package;\n}
14 . ($file ? "#line $line \"$file\"\n" : '')
15 . 'sub { my $m = splice @_, 1, 1; shift->$m(@_) };'."\n";
16 my $sub = \(eval $code
17 or die "Couldn't build importer for $package: $@");
18 $importers{$target} = $sub
24 my ($class, $target, @args) = @_;
25 $class->${_importer($target)}(import => @args);
28 sub unimport::out_of {
29 my ($class, $target, @args) = @_;
30 $class->${_importer($target)}(unimport => @args);
37 Import::Into - import packages into other packages
41 package My::MultiExporter;
50 Thing1->import::into($target);
51 Thing2->import::into($target, qw(import arguments));
54 Note: you don't need to do anything more clever than this provided you
55 document that people wanting to re-export your module should also be using
56 L<Import::Into>. In fact, for a single module you can simply do:
60 Thing1->import::into(scalar caller);
65 use base qw(Exporter);
68 shift->export_to_level(1);
69 Thing1->import::into(scalar caller);
72 Note 2: You do B<not> need to do anything to Thing1 to be able to call
73 C<import::into> on it. This is a global method, and is callable on any
74 package (and in fact on any object as well, although it's rarer that you'd
77 Finally, we also provide an C<unimport::out_of> to allow the exporting of the
80 # unimport::out_of was added in 1.1.0 (1.001000)
82 Moose->unimport::out_of(scalar caller); # no MyThing == no Moose
85 If how and why this all works is of interest to you, please read on to the
86 description immediately below.
90 Writing exporters is a pain. Some use L<Exporter>, some use L<Sub::Exporter>,
91 some use L<Moose::Exporter>, some use L<Exporter::Declare> ... and some things
94 If you want to re-export other things, you have to know which is which.
95 L<Exporter> subclasses provide export_to_level, but if they overrode their
96 import method all bets are off. L<Sub::Exporter> provides an into parameter
97 but figuring out something used it isn't trivial. Pragmas need to have
98 their C<import> method called directly since they affect the current unit of
103 However, there is an approach that actually works for all of these types.
105 eval "package $target; use $thing;"
107 will work for anything checking caller, which is everything except pragmas.
108 But it doesn't work for pragmas - pragmas need:
112 because they're designed to affect the code currently being compiled - so
113 within an eval, that's the scope of the eval itself, not the module that
114 just C<use>d you - so
120 doesn't do what you wanted, but
126 will apply L<strict> to the calling file correctly.
128 Of course, now you have two new problems - first, that you still need to
129 know if something's a pragma, and second that you can't use either of
130 these approaches alone on something like L<Moose> or L<Moo> that's both
131 an exporter and a pragma.
133 So, the complete solution is:
135 my $sub = eval "package $target; sub { shift->import(\@_) }";
136 $sub->($thing, @import_args);
138 which means that import is called from the right place for pragmas to take
139 effect, and from the right package for caller checking to work - and so
140 behaves correctly for all types of exporter, for pragmas, and for hybrids.
142 Remembering all this, however, is excessively irritating. So I wrote a module
143 so I didn't have to anymore. Loading L<Import::Into> creates a global method
144 C<import::into> which you can call on any package to import it into another
145 package. So now you can simply write:
149 $thing->import::into($target, @import_args);
151 This works because of how perl resolves method calls - a call to a simple
152 method name is resolved against the package of the class or object, so
154 $thing->method_name(@args);
156 is roughly equivalent to:
158 my $code_ref = $thing->can('method_name');
159 $code_ref->($thing, @args);
161 while if a C<::> is found, the lookup is made relative to the package name
162 (i.e. everything before the last C<::>) so
164 $thing->Package::Name::method_name(@args);
166 is roughly equivalent to:
168 my $code_ref = Package::Name->can('method_name');
169 $code_ref->($thing, @args);
171 So since L<Import::Into> defines a method C<into> in package C<import>
172 the syntax reliably calls that.
174 For more craziness of this order, have a look at the article I wrote at
175 L<http://shadow.cat/blog/matt-s-trout/madness-with-methods> which covers
176 coderef abuse and the C<${\...}> syntax.
178 Final note: You do still need to ensure that you already loaded C<$thing> - if
179 you're receiving this from a parameter, I recommend using L<Module::Runtime>:
182 use Module::Runtime qw(use_module);
184 use_module($thing)->import::into($target, @import_args);
188 =head1 ACKNOWLEDGEMENTS
190 Thanks to Getty for asking "how can I get C<< use strict; use warnings; >>
191 turned on for all consumers of my code?" and then "why is this not a
196 mst - Matt S. Trout (cpan:MSTROUT) <mst@shadowcat.co.uk>
200 None yet - maybe this software is perfect! (ahahahahahahahahaha)
204 Copyright (c) 2012 the Import::Into L</AUTHOR> and L</CONTRIBUTORS>
209 This library is free software and may be distributed under the same terms