use strict;
use warnings;
-use Carp qw/croak/;
-
=head1 NAME
Variable::Magic - Associate user-defined magic to variables from Perl.
=head1 VERSION
-Version 0.40
+Version 0.46
=cut
our $VERSION;
BEGIN {
- $VERSION = '0.40';
+ $VERSION = '0.46';
}
=head1 SYNOPSIS
- use Variable::Magic qw/wizard cast VMG_OP_INFO_NAME/;
+ use Variable::Magic qw<wizard cast VMG_OP_INFO_NAME>;
{ # A variable tracer
- my $wiz = wizard set => sub { print "now set to ${$_[0]}!\n" },
- free => sub { print "destroyed!\n" };
+ my $wiz = wizard(
+ set => sub { print "now set to ${$_[0]}!\n" },
+ free => sub { print "destroyed!\n" },
+ );
my $a = 1;
cast $a, $wiz;
} # "destroyed!"
{ # A hash with a default value
- my $wiz = wizard data => sub { $_[1] },
- fetch => sub { $_[2] = $_[1] unless exists $_[0]->{$_[2]}; () },
- store => sub { print "key $_[2] stored in $_[-1]\n" },
- copy_key => 1,
- op_info => VMG_OP_INFO_NAME;
+ my $wiz = wizard(
+ data => sub { $_[1] },
+ fetch => sub { $_[2] = $_[1] unless exists $_[0]->{$_[2]}; () },
+ store => sub { print "key $_[2] stored in $_[-1]\n" },
+ copy_key => 1,
+ op_info => VMG_OP_INFO_NAME,
+ );
my %h = (_default => 0, apple => 2);
cast %h, $wiz, '_default';
- print $h{banana}, "\n"; # "0", because the 'banana' key doesn't exist in %h
+ print $h{banana}, "\n"; # "0" (there is no 'banana' key in %h)
$h{pear} = 1; # "key pear stored in helem"
}
=head1 DESCRIPTION
-Magic is Perl way of enhancing objects.
-This mechanism lets the user add extra data to any variable and hook syntaxical operations (such as access, assignment or destruction) that can be applied to it.
+Magic is Perl's way of enhancing variables.
+This mechanism lets the user add extra data to any variable and hook syntactical operations (such as access, assignment or destruction) that can be applied to it.
With this module, you can add your own magic to any variable without having to write a single line of XS.
You'll realize that these magic variables look a lot like tied variables.
It doesn't replace the original semantics.
-Magic callbacks usually trigger before the original action take place, and can't prevent it to happen.
+Magic callbacks usually get triggered before the original action takes place, and can't prevent it from happening.
This also makes catching individual events easier than with C<tie>, where you have to provide fallbacks methods for all actions by usually inheriting from the correct C<Tie::Std*> class and overriding individual methods in your own class.
=item *
=back
-The following actions only apply to hashes and are available iff C<VMG_UVAR> is true.
+The following actions only apply to hashes and are available iff L</VMG_UVAR> is true.
They are referred to as C<uvar> magics.
=over 4
=head2 C<wizard>
- wizard data => sub { ... },
- get => sub { my ($ref, $data [, $op]) = @_; ... },
- set => sub { my ($ref, $data [, $op]) = @_; ... },
- len => sub { my ($ref, $data, $len [, $op]) = @_; ... ; return $newlen; },
- clear => sub { my ($ref, $data [, $op]) = @_; ... },
- free => sub { my ($ref, $data [, $op]) = @_, ... },
- copy => sub { my ($ref, $data, $key, $elt [, $op]) = @_; ... },
- local => sub { my ($ref, $data [, $op]) = @_; ... },
- fetch => sub { my ($ref, $data, $key [, $op]) = @_; ... },
- store => sub { my ($ref, $data, $key [, $op]) = @_; ... },
- exists => sub { my ($ref, $data, $key [, $op]) = @_; ... },
- delete => sub { my ($ref, $data, $key [, $op]) = @_; ... },
- copy_key => $bool,
- op_info => [ 0 | VMG_OP_INFO_NAME | VMG_OP_INFO_OBJECT ]
+ wizard(
+ data => sub { ... },
+ get => sub { my ($ref, $data [, $op]) = @_; ... },
+ set => sub { my ($ref, $data [, $op]) = @_; ... },
+ len => sub {
+ my ($ref, $data, $len [, $op]) = @_; ... ; return $newlen
+ },
+ clear => sub { my ($ref, $data [, $op]) = @_; ... },
+ free => sub { my ($ref, $data [, $op]) = @_, ... },
+ copy => sub { my ($ref, $data, $key, $elt [, $op]) = @_; ... },
+ local => sub { my ($ref, $data [, $op]) = @_; ... },
+ fetch => sub { my ($ref, $data, $key [, $op]) = @_; ... },
+ store => sub { my ($ref, $data, $key [, $op]) = @_; ... },
+ exists => sub { my ($ref, $data, $key [, $op]) = @_; ... },
+ delete => sub { my ($ref, $data, $key [, $op]) = @_; ... },
+ copy_key => $bool,
+ op_info => [ 0 | VMG_OP_INFO_NAME | VMG_OP_INFO_OBJECT ],
+ )
This function creates a 'wizard', an opaque type that holds the magic information.
It takes a list of keys / values as argument, whose keys can be :
Here's a simple usage example :
# A simple scalar tracer
- my $wiz = wizard get => sub { print STDERR "got ${$_[0]}\n" },
- set => sub { print STDERR "set to ${$_[0]}\n" },
- free => sub { print STDERR "${$_[0]} was deleted\n" }
+ my $wiz = wizard(
+ get => sub { print STDERR "got ${$_[0]}\n" },
+ set => sub { print STDERR "set to ${$_[0]}\n" },
+ free => sub { print STDERR "${$_[0]} was deleted\n" },
+ );
=cut
sub wizard {
- croak 'Wrong number of arguments for wizard()' if @_ % 2;
+ if (@_ % 2) {
+ require Carp;
+ Carp::croak('Wrong number of arguments for wizard()');
+ }
+
my %opts = @_;
- my @keys = qw/data op_info get set len clear free/;
+
+ my @keys = qw<op_info data get set len clear free>;
push @keys, 'copy' if MGf_COPY;
push @keys, 'dup' if MGf_DUP;
push @keys, 'local' if MGf_LOCAL;
- push @keys, qw/fetch store exists delete copy_key/ if VMG_UVAR;
- my $ret = eval { _wizard(map $opts{$_}, @keys) };
- if (my $err = $@) {
+ push @keys, qw<fetch store exists delete copy_key> if VMG_UVAR;
+
+ my ($wiz, $err);
+ {
+ local $@;
+ $wiz = eval { _wizard(map $opts{$_}, @keys) };
+ $err = $@;
+ }
+ if ($err) {
$err =~ s/\sat\s+.*?\n//;
- croak $err;
+ require Carp;
+ Carp::croak($err);
}
- return $ret;
+
+ return $wiz;
}
=head2 C<cast>
=head2 C<VMG_UVAR>
When this constant is true, you can use the C<fetch,store,exists,delete> callbacks on hashes.
+Initial VMG_UVAR capability was introduced in perl 5.9.5, with a fully functional implementation
+shipped with perl 5.10.0.
=head2 C<VMG_COMPAT_ARRAY_PUSH_NOLEN>
True for perls that don't call 'len' magic when taking the C<length> of a magical scalar.
+=head2 C<VMG_COMPAT_GLOB_GET>
+
+True for perls that call 'get' magic for operations on globs.
+
=head2 C<VMG_PERL_PATCHLEVEL>
The perl patchlevel this module was built with, or C<0> for non-debugging perls.
=head2 Associate an object to any perl variable
-This can be useful for passing user data through limited APIs.
+This technique can be useful for passing user data through limited APIs.
+It is similar to using inside-out objects, but without the drawback of having to implement a complex destructor.
{
package Magical::UserData;
- use Variable::Magic qw/wizard cast getdata/;
+ use Variable::Magic qw<wizard cast getdata>;
my $wiz = wizard data => sub { \$_[1] };
my ($var) = @_;
my $data = &getdata($var, $wiz);
unless (defined $data) {
- &cast($var, $wiz);
- $data = &getdata($var, $wiz);
- die "Couldn't cast UserData magic onto the variable" unless defined $data;
+ $data = \(my $slot);
+ &cast($var, $wiz, $slot)
+ or die "Couldn't cast UserData magic onto the variable";
}
$$data;
}
=cut
-use base qw/Exporter/;
+use base qw<Exporter>;
our @EXPORT = ();
our %EXPORT_TAGS = (
- 'funcs' => [ qw/wizard cast getdata dispell/ ],
- 'consts' => [
- qw/MGf_COPY MGf_DUP MGf_LOCAL VMG_UVAR/,
- qw/VMG_COMPAT_ARRAY_PUSH_NOLEN VMG_COMPAT_ARRAY_PUSH_NOLEN_VOID/,
- qw/VMG_COMPAT_ARRAY_UNSHIFT_NOLEN_VOID/,
- qw/VMG_COMPAT_ARRAY_UNDEF_CLEAR/,
- qw/VMG_COMPAT_SCALAR_LENGTH_NOLEN/,
- qw/VMG_PERL_PATCHLEVEL/,
- qw/VMG_THREADSAFE VMG_FORKSAFE/,
- qw/VMG_OP_INFO_NAME VMG_OP_INFO_OBJECT/
- ]
+ 'funcs' => [ qw<wizard cast getdata dispell> ],
+ 'consts' => [ qw<
+ MGf_COPY MGf_DUP MGf_LOCAL VMG_UVAR
+ VMG_COMPAT_ARRAY_PUSH_NOLEN VMG_COMPAT_ARRAY_PUSH_NOLEN_VOID
+ VMG_COMPAT_ARRAY_UNSHIFT_NOLEN_VOID
+ VMG_COMPAT_ARRAY_UNDEF_CLEAR
+ VMG_COMPAT_SCALAR_LENGTH_NOLEN
+ VMG_COMPAT_GLOB_GET
+ VMG_PERL_PATCHLEVEL
+ VMG_THREADSAFE VMG_FORKSAFE
+ VMG_OP_INFO_NAME VMG_OP_INFO_OBJECT
+ > ],
);
our @EXPORT_OK = map { @$_ } values %EXPORT_TAGS;
$EXPORT_TAGS{'all'} = [ @EXPORT_OK ];
If you define a wizard with a C<free> callback and cast it on itself, this destructor won't be called because the wizard will be destroyed first.
+In order to define magic on hash members, you need at least L<perl> 5.10.0 (see L</VMG_UVAR>)
+
=head1 DEPENDENCIES
L<perl> 5.8.
+A C compiler.
+This module may happen to build with a C++ compiler as well, but don't rely on it, as no guarantee is made in this regard.
+
L<Carp> (standard since perl 5), L<XSLoader> (standard since perl 5.006).
Copy tests need L<Tie::Array> (standard since perl 5.005) and L<Tie::Hash> (since 5.002).
=head1 COPYRIGHT & LICENSE
-Copyright 2007,2008,2009,2010 Vincent Pit, all rights reserved.
+Copyright 2007,2008,2009,2010,2011 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.
projects / perl / modules / Variable-Magic.git / blobdiff