=head1 VERSION
-Version 0.31
+Version 0.32
=cut
our $VERSION;
BEGIN {
- $VERSION = '0.31';
+ $VERSION = '0.32';
}
=head1 SYNOPSIS
With this module, you can add your own magic to any variable without having to write a single line of XS.
You'll realize that these magic variables look a lot like tied variables.
-It's not surprising, as tied variables are implemented as a special kind of magic, just like any 'irregular' Perl variable : scalars like C<$!>, C<$(> or C<$^W>, the C<%ENV> and C<%SIG> hashes, the C<@ISA> array, C<vec()> and C<substr()> lvalues, L<thread::shared> variables...
+It's not surprising, as tied variables are implemented as a special kind of magic, just like any 'irregular' Perl variable : scalars like C<$!>, C<$(> or C<$^W>, the C<%ENV> and C<%SIG> hashes, the C<@ISA> array, C<vec()> and C<substr()> lvalues, L<threads::shared> variables...
They all share the same underlying C API, and this module gives you direct access to it.
Still, the magic made available by this module differs from tieing and overloading in several ways :
C<clear>
-This magic is invoked when the variable is reset, such as when an array is emptied.
+This magic is invoked when a container variable is reset, i.e. when an array or a hash is emptied.
Please note that this is different from undefining the variable, even though the magic is called when the clearing is a result of the undefine (e.g. for an array, but actually a bug prevent it to work before perl 5.9.5 - see the L<history|/PERL MAGIC HISTORY>).
=item *
You can refer to the tests to have more insight of where the different magics are invoked.
To prevent any clash between different magics defined with this module, an unique numerical signature is attached to each kind of magic (i.e. each set of callbacks for magic operations).
+At the C level, magic tokens owned by magic created by this module have their C<< mg->mg_private >> field set to C<0x3891> or C<0x3892>, so please don't use these magic (sic) numbers in other extensions.
=head1 FUNCTIONS
set => sub { print STDERR "set to ${$_[0]}\n" },
free => sub { print STDERR "${$_[0]} was deleted\n" }
+Note that C<free> callbacks are I<never> called during global destruction, as there's no way to ensure that the wizard and the C<free> callback weren't destroyed before the variable.
+
=cut
sub wizard {
This function associates C<$wiz> magic to the variable supplied, without overwriting any other kind of magic.
You can also supply the numeric signature C<$sig> instead of C<$wiz>.
-It returns true on success or when C<$wiz> magic is already present, C<0> on error, and C<undef> when no magic corresponds to the given signature (in case C<$sig> was supplied).
-All extra arguments specified after C<$wiz> are passed to the private data constructor.
+It returns true on success or when C<$wiz> magic is already present, and croaks on error or when no magic corresponds to the given signature (in case a C<$sig> was supplied).
+All extra arguments specified after C<$wiz> are passed to the private data constructor in C<@_[1 .. @_-1]>.
If the variable isn't a hash, any C<uvar> callback of the wizard is safely ignored.
- # Casts $wiz onto $x. If $wiz isn't a signature, undef can't be returned.
+ # Casts $wiz onto $x, and pass '1' to the data constructor.
my $x;
- die 'error' unless cast $x, $wiz;
+ cast $x, $wiz, 1;
The C<var> argument can be an array or hash value.
Magic for those behaves like for any other scalar, except that it is dispelled when the entry is deleted from the container.
getdata [$@%&*]var, [$wiz|$sig]
This accessor fetches the private data associated with the magic C<$wiz> (or the signature C<$sig>) in the variable.
-C<undef> is returned when no such magic or data is found, or when C<$sig> does not represent a current valid magic object.
+It croaks when C<$wiz> or C<$sig> do not represent a current valid magic object attached to the variable, and returns C<undef> when the wizard has no data constructor or when the data is actually C<undef>.
- # Get the attached data.
- my $data = getdata $x, $wiz or die 'no such magic or magic has no data';
+ # Get the attached data, or undef if the wizard does not attach any.
+ my $data = getdata $x, $wiz;
=head2 C<dispell>
The exact opposite of L</cast> : it dissociates C<$wiz> magic from the variable.
You can also pass the magic signature C<$sig> as the second argument.
-True is returned on success, C<0> on error or when no magic represented by C<$wiz> could be found in the variable, and C<undef> when no magic corresponds to the given signature (in case C<$sig> was supplied).
+This function returns true on success, C<0> when no magic represented by C<$wiz> or C<$sig> could be found in the variable, and croaks if the supplied wizard or signature is invalid.
- # Dispell now. If $wiz isn't a signature, undef can't be returned.
- die 'no such magic or error' unless dispell $x, $wiz;
+ # Dispell now.
+ die 'no such magic in $x' unless dispell $x, $wiz;
=head1 CONSTANTS
projects / perl / modules / Variable-Magic.git / blobdiff