documentationtality

[p5sagit/Import-Into.git] / lib / Import / Into.pm

diff --git a/lib/Import/Into.pm b/lib/Import/Into.pm
index a8a3ada..d89231a 100644 (file)
--- a/lib/Import/Into.pm
+++ b/lib/Import/Into.pm
@@ -27,6 +27,8 @@ Import::Into - import packages into other packages
 
   package My::MultiExporter;
 
+  use Import::Into;
+
   use Thing1 ();
   use Thing2 ();
 
@@ -36,10 +38,65 @@ Import::Into - import packages into other packages
     Thing2->import::into($target, qw(import arguments));
   }
 
+=head1 DESCRIPTION
+
+Writing exporters is a pain. Some use L<Exporter>, some use L<Sub::Exporter>,
+some use L<Moose::Exporter>, some use L<Exporter::Declare> ... and some things
+are pragmas.
+
+If you want to re-export other things, you have to know which is which.
+L<Exporter> subclasses provide export_to_level, but if they overrode their
+import method all bets are off. L<Sub::Exporter> provides an into parameter
+but figuring out something used it isn't trivial. Pragmas need to have
+their C<import> method called directly since they affect the current unit of
+compilation.
+
+It's ... annoying.
+
+However, there is an approach that actually works for all of these types.
+
+  eval "package $target; use $thing;"
+
+will work for anything checking caller, which is everything except pragmas.
+But it doesn't work for pragmas - pragmas need:
+
+  $thing->import;
+
+So, the solution is:
+
+  my $sub = eval "package $target; sub { shift->import(\@_) }";
+  $sub->($thing, @import_args);
+
+which means that import is called from the right place for pragmas to take
+effect, and from the right package for caller checking to work.
+
+Remembering all this, however, is excessively irritating. So I wrote a module
+so I didn't have to anymore. Loading L<Import::Into> will create a method
+C<import::into> which you can call on a package to import it into another
+package. So now you can simply write:
+
+  use Import::Into;
+
+  $thing->import::into($target, @import_args);
+
+Just make sure you already loaded C<$thing> - if you're receiving this from
+a parameter, I recommend using L<Module::Runtime>:
+
+  use Import::Into;
+  use Module::Runtime qw(use_module);
+
+  use_module($thing)->import::into($target, @import_args);
+
+And that's it.
+
 =head1 AUTHOR
 
 mst - Matt S. Trout (cpan:MSTROUT) <mst@shadowcat.co.uk>
 
+=head1 CONTRIBUTORS
+
+None yet - maybe this software is perfect! (ahahahahahahahahaha)
+
 =head1 COPYRIGHT
 
 Copyright (c) 2010-2011 the Import::Into L</AUTHOR> and L</CONTRIBUTORS>