4 use warnings FATAL => 'all';
6 our $VERSION = '1.001001'; # 1.1.1
12 my ($package, $file, $line)
13 = $target =~ /[^0-9]/ ? ($target) : caller($target + 1);
14 my $code = qq{package $package;\n}
15 . ($file ? "#line $line \"$file\"\n" : '')
16 . 'sub { my $m = splice @_, 1, 1; shift->$m(@_) };'."\n";
17 my $sub = \(eval $code
18 or die "Couldn't build importer for $package: $@");
19 $importers{$target} = $sub
25 my ($class, $target, @args) = @_;
26 $class->${_importer($target)}(import => @args);
29 sub unimport::out_of {
30 my ($class, $target, @args) = @_;
31 $class->${_importer($target)}(unimport => @args);
38 Import::Into - import packages into other packages
42 package My::MultiExporter;
51 Thing1->import::into($target);
52 Thing2->import::into($target, qw(import arguments));
55 Note: you don't need to do anything more clever than this provided you
56 document that people wanting to re-export your module should also be using
57 L<Import::Into>. In fact, for a single module you can simply do:
61 Thing1->import::into(scalar caller);
66 use base qw(Exporter);
69 shift->export_to_level(1);
70 Thing1->import::into(scalar caller);
73 Note 2: You do B<not> need to do anything to Thing1 to be able to call
74 C<import::into> on it. This is a global method, and is callable on any
75 package (and in fact on any object as well, although it's rarer that you'd
78 Finally, we also provide an C<unimport::out_of> to allow the exporting of the
81 # unimport::out_of was added in 1.1.0 (1.001000)
83 Moose->unimport::out_of(scalar caller); # no MyThing == no Moose
86 If how and why this all works is of interest to you, please read on to the
87 description immediately below.
91 Writing exporters is a pain. Some use L<Exporter>, some use L<Sub::Exporter>,
92 some use L<Moose::Exporter>, some use L<Exporter::Declare> ... and some things
95 If you want to re-export other things, you have to know which is which.
96 L<Exporter> subclasses provide export_to_level, but if they overrode their
97 import method all bets are off. L<Sub::Exporter> provides an into parameter
98 but figuring out something used it isn't trivial. Pragmas need to have
99 their C<import> method called directly since they affect the current unit of
104 However, there is an approach that actually works for all of these types.
106 eval "package $target; use $thing;"
108 will work for anything checking caller, which is everything except pragmas.
109 But it doesn't work for pragmas - pragmas need:
113 because they're designed to affect the code currently being compiled - so
114 within an eval, that's the scope of the eval itself, not the module that
115 just C<use>d you - so
121 doesn't do what you wanted, but
127 will apply L<strict> to the calling file correctly.
129 Of course, now you have two new problems - first, that you still need to
130 know if something's a pragma, and second that you can't use either of
131 these approaches alone on something like L<Moose> or L<Moo> that's both
132 an exporter and a pragma.
134 So, the complete solution is:
136 my $sub = eval "package $target; sub { shift->import(\@_) }";
137 $sub->($thing, @import_args);
139 which means that import is called from the right place for pragmas to take
140 effect, and from the right package for caller checking to work - and so
141 behaves correctly for all types of exporter, for pragmas, and for hybrids.
143 Remembering all this, however, is excessively irritating. So I wrote a module
144 so I didn't have to anymore. Loading L<Import::Into> creates a global method
145 C<import::into> which you can call on any package to import it into another
146 package. So now you can simply write:
150 $thing->import::into($target, @import_args);
152 This works because of how perl resolves method calls - a call to a simple
153 method name is resolved against the package of the class or object, so
155 $thing->method_name(@args);
157 is roughly equivalent to:
159 my $code_ref = $thing->can('method_name');
160 $code_ref->($thing, @args);
162 while if a C<::> is found, the lookup is made relative to the package name
163 (i.e. everything before the last C<::>) so
165 $thing->Package::Name::method_name(@args);
167 is roughly equivalent to:
169 my $code_ref = Package::Name->can('method_name');
170 $code_ref->($thing, @args);
172 So since L<Import::Into> defines a method C<into> in package C<import>
173 the syntax reliably calls that.
175 For more craziness of this order, have a look at the article I wrote at
176 L<http://shadow.cat/blog/matt-s-trout/madness-with-methods> which covers
177 coderef abuse and the C<${\...}> syntax.
179 Final note: You do still need to ensure that you already loaded C<$thing> - if
180 you're receiving this from a parameter, I recommend using L<Module::Runtime>:
183 use Module::Runtime qw(use_module);
185 use_module($thing)->import::into($target, @import_args);
189 =head1 ACKNOWLEDGEMENTS
191 Thanks to Getty for asking "how can I get C<< use strict; use warnings; >>
192 turned on for all consumers of my code?" and then "why is this not a
197 mst - Matt S. Trout (cpan:MSTROUT) <mst@shadowcat.co.uk>
201 haarg - Graham Knop (cpan:HAARG) <haarg@haarg.org>
205 Copyright (c) 2012 the Import::Into L</AUTHOR> and L</CONTRIBUTORS>
210 This library is free software and may be distributed under the same terms