X-Git-Url: http://git.vpit.fr/?a=blobdiff_plain;f=README;h=3a9cf67273197e679a7010a5401365dc3340e08a;hb=HEAD;hp=b10ea32ae8d3002cad4bf5842eddb182b843218d;hpb=810a63159661ab3e66c139d6f62fcd28f19ab7be;p=perl%2Fmodules%2FVariable-Magic.git

diff --git a/README b/README
index b10ea32..3a9cf67 100644
--- a/README
+++ b/README
@@ -2,7 +2,7 @@ NAME
     Variable::Magic - Associate user-defined magic to variables from Perl.
 
 VERSION
-    Version 0.57
+    Version 0.64
 
 SYNOPSIS
         use Variable::Magic qw<wizard cast VMG_OP_INFO_NAME>;
@@ -265,10 +265,17 @@ FUNCTIONS
         Both result in a small performance hit, but just getting the name is
         lighter than getting the op object.
 
-        These callbacks are executed in scalar context and are expected to
-        return an integer, which is then passed straight to the perl magic
-        API. However, only the return value of the *len* magic callback
-        currently holds a meaning.
+        These callbacks are always executed in scalar context. The returned
+        value is coerced into a signed integer, which is then passed
+        straight to the perl magic API. However, note that perl currently
+        only cares about the return value of the *len* magic callback and
+        ignores all the others. Starting with Variable::Magic 0.58, a
+        reference returned from a non-*len* magic callback will not be
+        destroyed immediately but will be allowed to survive until the end
+        of the statement that triggered the magic. This lets you use this
+        return value as a token for triggering a destructor after the
+        original magic action takes place. You can see an example of this
+        technique in the cookbook.
 
     Each callback can be specified as :
 
@@ -501,6 +508,45 @@ COOKBOOK
     Of course, this example does nothing with the values that are added
     after the "cast".
 
+  Delayed magic actions
+    Starting with Variable::Magic 0.58, the return value of the magic
+    callbacks can be used to delay the action until after the original
+    action takes place :
+
+        my $delayed;
+        my $delayed_aux = wizard(
+         data => sub { $_[1] },
+         free => sub {
+          my ($target) = $_[1];
+          my $target_data = &getdata($target, $delayed);
+          local $target_data->{guard} = 1;
+          if (ref $target eq 'SCALAR') {
+           my $orig = $$target;
+           $$target = $target_data->{mangler}->($orig);
+          }
+          return;
+         },
+        );
+        $delayed = wizard(
+         data => sub {
+          return +{ guard => 0, mangler => $_[1] };
+         },
+         set  => sub {
+          return if $_[1]->{guard};
+          my $token;
+          cast $token, $delayed_aux, $_[0];
+          return \$token;
+         },
+        );
+        my $x = 1;
+        cast $x, $delayed => sub { $_[0] * 2 };
+        $x = 2;
+        # $x is now 4
+        # But note that the delayed action only takes place at the end of the
+        # current statement :
+        my @y = ($x = 5, $x);
+        # $x is now 10, but @y is (5, 5)
+
 PERL MAGIC HISTORY
     The places where magic is invoked have changed a bit through perl
     history. Here is a little list of the most recent ones.
@@ -582,7 +628,7 @@ SEE ALSO
     perltie and overload for other ways of enhancing objects.
 
 AUTHOR
-    Vincent Pit, "<perl at profvince.com>", <http://www.profvince.com>.
+    Vincent Pit "<vpit at cpan.org>".
 
     You can contact me by mail or on "irc.perl.org" (vincent).
 
@@ -598,12 +644,10 @@ SUPPORT
 
         perldoc Variable::Magic
 
-    Tests code coverage report is available at
-    <http://www.profvince.com/perl/cover/Variable-Magic>.
-
 COPYRIGHT & LICENSE
-    Copyright 2007,2008,2009,2010,2011,2012,2013,2014,2015 Vincent Pit, all
-    rights reserved.
+    Copyright
+    2007,2008,2009,2010,2011,2012,2013,2014,2015,2016,2017,2022,2024 Vincent
+    Pit, all rights reserved.
 
     This program is free software; you can redistribute it and/or modify it
     under the same terms as Perl itself.