An example on how to cast magic recursively

[perl/modules/Variable-Magic.git] / lib / Variable / Magic.pm

diff --git a/lib/Variable/Magic.pm b/lib/Variable/Magic.pm
index 4359fef0976cc7c6b3ec1c4f4536a3259fad7f91..7b4034c5b2a00892e4ffc0b1515c6cb12e9f4656 100644 (file)
--- a/lib/Variable/Magic.pm
+++ b/lib/Variable/Magic.pm
@@ -336,6 +336,48 @@ For example, if you want to call C<POSIX::tzset> each time the C<'TZ'> environme
 
 If you want to overcome the possible deletion of the C<'TZ'> entry, you have no choice but to rely on C<store> uvar magic.
 
+C<cast> can be called from any magical callback, and in particular from C<data>.
+This allows you to recursively cast magic on datastructures :
+
+    my $wiz;
+    $wiz = wizard
+            data => sub {
+             my ($var, $depth) = @_;
+             $depth ||= 0;
+             my $r = ref $var;
+             if ($r eq 'ARRAY') {
+              &cast((ref() ? $_ : \$_), $wiz, $depth + 1) for @$var;
+             } elsif ($r eq 'HASH') {
+              &cast((ref() ? $_ : \$_), $wiz, $depth + 1) for values %$var;
+             }
+             return $depth;
+            },
+            free => sub {
+             my ($var, $depth) = @_;
+             my $r = ref $var;
+             print "free $r at depth $depth\n";
+             ();
+            };
+
+    {
+     my %h = (
+      a => [ 1, 2 ],
+      b => { c => 3 }
+     );
+     cast %h, $wiz;
+    }
+
+When C<%h> goes out of scope, this will print something among the lines of :
+
+    free HASH at depth 0
+    free HASH at depth 1
+    free SCALAR at depth 2
+    free ARRAY at depth 1
+    free SCALAR at depth 3
+    free SCALAR at depth 3
+
+Of course, this example does nothing with the values that are added after the C<cast>.
+
 =head2 C<getdata>
 
     getdata [$@%&*]var, [$wiz|$sig]