Variable::Magic - Associate user-defined magic to variables from Perl.
VERSION
- Version 0.38
+ Version 0.44
SYNOPSIS
use Variable::Magic qw/wizard cast VMG_OP_INFO_NAME/;
}
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
+ 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.
* It doesn't replace the original semantics.
- Magic callbacks usually trigger before the original action take
- place, and can't prevent it to happen. This also makes catching
- individual events easier than with "tie", where you have to provide
- fallbacks methods for all actions by usually inheriting from the
- correct "Tie::Std*" class and overriding individual methods in your
- own class.
+ 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 "tie", where you have to
+ provide fallbacks methods for all actions by usually inheriting from
+ the correct "Tie::Std*" class and overriding individual methods in
+ your own class.
* It's type-agnostic.
information. It takes a list of keys / values as argument, whose keys
can be :
- * "sig"
-
- The numerical signature. If not specified or undefined, a random
- signature is generated. If the signature matches an already defined
- magic, then the existant magic object is returned.
-
- This option is deprecated and will be removed in december 2009.
-
* "data"
- A code reference to a private data constructor. It is called each
- time this magic is cast on a variable, and the scalar returned is
- used as private data storage for it. $_[0] is a reference to the
- magic object and @_[1 .. @_-1] are all extra arguments that were
- passed to "cast".
+ A code (or string) reference to a private data constructor. It is
+ called each time this magic is cast on a variable, and the scalar
+ returned is used as private data storage for it. $_[0] is a
+ reference to the magic object and @_[1 .. @_-1] are all extra
+ arguments that were passed to "cast".
* "get", "set", "len", "clear", "free", "copy", "local", "fetch",
"store", "exists" and "delete"
- Code references to the corresponding magic callbacks. You don't have
- to specify all of them : the magic associated with undefined entries
- simply won't be hooked. In those callbacks, $_[0] is always a
- reference to the magic object and $_[1] is always the private data
- (or "undef" when no private data constructor was supplied).
+ Code (or string) references to the corresponding magic callbacks.
+ You don't have to specify all of them : the magic associated with
+ undefined entries simply won't be hooked. In those callbacks, $_[0]
+ is always a reference to the magic object and $_[1] is always the
+ private data (or "undef" when no private data constructor was
+ supplied).
Moreover, when you pass "op_info => $num" to "wizard", the last
element of @_ will be the current op name if "$num ==
straight to the perl magic API. However, only the return value of
the "len" callback currently holds a meaning.
- # 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" }
+ Each callback can be specified as a code or a string reference, in which
+ case the function denoted by the string will be used as the callback.
Note that "free" callbacks are *never* called during global destruction,
as there's no way to ensure that the wizard and the "free" callback
weren't destroyed before the variable.
- "gensig"
- With this tool, you can manually generate random magic signature between
- SIG_MIN and SIG_MAX inclusive. That's the way "wizard" creates them when
- no signature is supplied.
-
- # Generate a signature
- my $sig = gensig;
-
- This function is deprecated and will be removed in december 2009.
-
- "getsig"
- getsig $wiz
-
- This accessor returns the magic signature of this wizard.
-
- # Get $wiz signature
- my $sig = getsig $wiz;
+ Here's a simple usage example :
- This function is deprecated and will be removed in december 2009.
+ # 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" }
"cast"
cast [$@%&*]var, $wiz, ...
die 'no such magic in $x' unless dispell $x, $wiz;
CONSTANTS
- "SIG_MIN"
- The minimum integer used as a signature for user-defined magic.
-
- This constant is deprecated and will be removed in december 2009.
-
- "SIG_MAX"
- The maximum integer used as a signature for user-defined magic.
-
- This constant is deprecated and will be removed in december 2009.
-
- "SIG_NBR"
- SIG_NBR = SIG_MAX - SIG_MIN + 1
-
- This constant is deprecated and will be removed in december 2009.
-
"MGf_COPY"
Evaluates to true iff the 'copy' magic is available.
True for perls that don't call 'len' magic when taking the "length" of a
magical scalar.
+ "VMG_COMPAT_GLOB_GET"
+ True for perls that call 'get' magic for operations on globs.
+
"VMG_PERL_PATCHLEVEL"
The perl patchlevel this module was built with, or 0 for non-debugging
perls.
COOKBOOK
Associate an object to any perl variable
- This can be useful for passing user data through limited APIs.
+ This technique can be useful for passing user data through limited APIs.
+ It is similar to using inside-out objects, but without the drawback of
+ having to implement a complex destructor.
{
package Magical::UserData;
my ($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;
}
magical array in non-void context.
EXPORT
- The functions "wizard", "gensig", "getsig", "cast", "getdata" and
- "dispell" are only exported on request. All of them are exported by the
- tags ':funcs' and ':all'.
+ The functions "wizard", "cast", "getdata" and "dispell" are only
+ exported on request. All of them are exported by the tags ':funcs' and
+ ':all'.
All the constants are also only exported on request, either individually
or by the tags ':consts' and ':all'.
<http://www.profvince.com/perl/cover/Variable-Magic>.
COPYRIGHT & LICENSE
- Copyright 2007-2009 Vincent Pit, all rights reserved.
+ Copyright 2007,2008,2009,2010 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