4 use warnings FATAL => 'all';
6 our $VERSION = '1.001001'; # 1.1.1
12 \($importers{$target} ||= eval qq{
14 sub { my \$m = splice \@_, 1, 1; shift->\$m(\@_) };
15 } or die "Couldn't build importer for $target: $@")
20 my ($class, $target, @args) = @_;
21 $class->${_importer($target)}(import => @args);
24 sub unimport::out_of {
25 my ($class, $target, @args) = @_;
26 $class->${_importer($target)}(unimport => @args);
33 Import::Into - import packages into other packages
37 package My::MultiExporter;
46 Thing1->import::into($target);
47 Thing2->import::into($target, qw(import arguments));
50 Note: you don't need to do anything more clever than this provided you
51 document that people wanting to re-export your module should also be using
52 L<Import::Into>. In fact, for a single module you can simply do:
56 Thing1->import::into(scalar caller);
61 use base qw(Exporter);
64 shift->export_to_level(1);
65 Thing1->import::into(scalar caller);
68 Note 2: You do B<not> need to do anything to Thing1 to be able to call
69 C<import::into> on it. This is a global method, and is callable on any
70 package (and in fact on any object as well, although it's rarer that you'd
73 Finally, we also provide an C<unimport::out_of> to allow the exporting of the
76 # unimport::out_of was added in 1.1.0 (1.001000)
78 Moose->unimport::out_of(scalar caller); # no MyThing == no Moose
81 If how and why this all works is of interest to you, please read on to the
82 description immediately below.
86 Writing exporters is a pain. Some use L<Exporter>, some use L<Sub::Exporter>,
87 some use L<Moose::Exporter>, some use L<Exporter::Declare> ... and some things
90 If you want to re-export other things, you have to know which is which.
91 L<Exporter> subclasses provide export_to_level, but if they overrode their
92 import method all bets are off. L<Sub::Exporter> provides an into parameter
93 but figuring out something used it isn't trivial. Pragmas need to have
94 their C<import> method called directly since they affect the current unit of
99 However, there is an approach that actually works for all of these types.
101 eval "package $target; use $thing;"
103 will work for anything checking caller, which is everything except pragmas.
104 But it doesn't work for pragmas - pragmas need:
108 because they're designed to affect the code currently being compiled - so
109 within an eval, that's the scope of the eval itself, not the module that
110 just C<use>d you - so
116 doesn't do what you wanted, but
122 will apply L<strict> to the calling file correctly.
124 Of course, now you have two new problems - first, that you still need to
125 know if something's a pragma, and second that you can't use either of
126 these approaches alone on something like L<Moose> or L<Moo> that's both
127 an exporter and a pragma.
129 So, the complete solution is:
131 my $sub = eval "package $target; sub { shift->import(\@_) }";
132 $sub->($thing, @import_args);
134 which means that import is called from the right place for pragmas to take
135 effect, and from the right package for caller checking to work - and so
136 behaves correctly for all types of exporter, for pragmas, and for hybrids.
138 Remembering all this, however, is excessively irritating. So I wrote a module
139 so I didn't have to anymore. Loading L<Import::Into> creates a global method
140 C<import::into> which you can call on any package to import it into another
141 package. So now you can simply write:
145 $thing->import::into($target, @import_args);
147 This works because of how perl resolves method calls - a call to a simple
148 method name is resolved against the package of the class or object, so
150 $thing->method_name(@args);
152 is roughly equivalent to:
154 my $code_ref = $thing->can('method_name');
155 $code_ref->($thing, @args);
157 while if a C<::> is found, the lookup is made relative to the package name
158 (i.e. everything before the last C<::>) so
160 $thing->Package::Name::method_name(@args);
162 is roughly equivalent to:
164 my $code_ref = Package::Name->can('method_name');
165 $code_ref->($thing, @args);
167 So since L<Import::Into> defines a method C<into> in package C<import>
168 the syntax reliably calls that.
170 For more craziness of this order, have a look at the article I wrote at
171 L<http://shadow.cat/blog/matt-s-trout/madness-with-methods> which covers
172 coderef abuse and the C<${\...}> syntax.
174 Final note: You do still need to ensure that you already loaded C<$thing> - if
175 you're receiving this from a parameter, I recommend using L<Module::Runtime>:
178 use Module::Runtime qw(use_module);
180 use_module($thing)->import::into($target, @import_args);
186 mst - Matt S. Trout (cpan:MSTROUT) <mst@shadowcat.co.uk>
190 None yet - maybe this software is perfect! (ahahahahahahahahaha)
194 Copyright (c) 2012 the Import::Into L</AUTHOR> and L</CONTRIBUTORS>
199 This library is free software and may be distributed under the same terms