Variable::Magic - Associate user-defined magic to variables from Perl.
VERSION
- Version 0.07_02
+ Version 0.08
SYNOPSIS
use Variable::Magic qw/wizard cast dispell/;
prevent it to work before perl 5.9.5 - see the history).
"free"
- This last one can be considered as an object destructor. It happens
- when the variable goes out of scope (with the exception of global
- scope), but not when it is undefined.
+ This one can be considered as an object destructor. It happens when
+ the variable goes out of scope (with the exception of global scope),
+ but not when it is undefined.
+
+ "copy"
+ This magic only applies to tied arrays and hashes. It fires when you
+ try to access or change their elements. It is available on your perl
+ iff "MGf_COPY" is true.
+
+ "dup"
+ Invoked when the variable is cloned across threads. Currently not
+ available.
+
+ "local"
+ When this magic is set on a variable, all subsequent localizations
+ of the variable will trigger the callback. It is available on your
+ perl iff "MGf_LOCAL" is true.
+
+ The following actions only applies to hashes and are available iff
+ "VMG_UVAR" is true. They are referred to as "uvar" magics.
+
+ "fetch"
+ This magic happens each time an element is fetched from the hash.
+
+ "store"
+ This one is called when an element is stored into the hash.
+
+ "exists"
+ This magic fires when a key is tested for existence in the hash.
+
+ "delete"
+ This last one triggers when a key is deleted in the hash, regardless
+ of whether the key actually exists in it.
+
+ 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.
The places where magic is invoked have changed a bit through perl
history. Here's a little list of the most recent ones.
+ 5.6.x
+ *p14416* : 'copy' and 'dup' magic.
+
5.9.3
'len' magic is no longer called when pushing an element into a magic
array.
+ *p26569* : 'local' magic.
5.9.5
- 'clear' magic wasn't invoked when undefining an array. The bug is fixed
- as of this version.
+ *p31064* : Meaningful 'uvar' magic.
+ *p31473* : 'clear' magic wasn't invoked when undefining an array. The
+ bug is fixed as of this version.
CONSTANTS
"SIG_MIN"
SIG_NBR = SIG_MAX - SIG_MIN + 1
"MGf_COPY"
- True iff the 'copy' magic is available.
+ Evaluates to true iff the 'copy' magic is available.
"MGf_DUP"
- True iff the 'dup' magic is available.
+ Evaluates to true iff the 'dup' magic is available.
"MGf_LOCAL"
- True iff the 'local' magic is available.
+ Evaluates to true iff the 'local' magic is available.
+
+ "VMG_UVAR"
+ When this constant is true, you can use the "fetch,store,exists,delete"
+ callbacks on hashes.
FUNCTIONS
"wizard"
- wizard sig => .., data => ..., get => .., set => .., len => .., clear => .., free => ..
+ wizard sig => ...,
+ data => sub { ... },
+ get => sub { my ($ref, $data) = @_; ... },
+ set => sub { my ($ref, $data) = @_; ... },
+ len => sub { my ($ref, $data, $len) = @_; ... ; return $newlen; },
+ clear => sub { my ($ref, $data) = @_; ... },
+ free => sub { my ($ref, $data) = @_, ... },
+ copy => sub { my ($ref, $data, $elt) = @_; ... },
+ local => sub { my ($ref, $data) = @_; ... },
+ fetch => sub { my ($ref, $data, $key) = @_; ... },
+ store => sub { my ($ref, $data, $key) = @_; ... },
+ exists => sub { my ($ref, $data, $key) = @_; ... },
+ delete => sub { my ($ref, $data, $key) = @_; ... }
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 :
- 'sig'
+ "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.
- 'data'
+ "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".
- 'get', 'set', 'len', 'clear' and 'free'
+ "get", "set", "len", "clear", "free", "copy", "local", "fetch", "store",
+ "exists" and "delete"
Code references to 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 a reference to
- the magic object and $_[1] is the private data (or "undef" when no
- private data constructor was supplied). In the special case of "len"
- magic and when the variable is an array, $_[2] contains its normal
- length.
+ 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). In the
+ special case of "len" magic and when the variable is an array, $_[2]
+ contains its normal length. "copy" magic receives the current
+ element (i.e. the value) in $_[2]. $_[2] is also the current key in
+ "fetch", "store", "exists" and "delete" callbacks.
# A simple scalar tracer
my $wiz = wizard get => sub { print STDERR "got ${$_[0]}\n" },
"dispell" are only exported on request. All of them are exported by the
tags ':funcs' and ':all'.
- The constants "SIG_MIN", "SIG_MAX" and "SIG_NBR" are also only exported
- on request. They are all exported by the tags ':consts' and ':all'.
+ The constants "SIG_MIN", "SIG_MAX", "SIG_NBR", "MGf_COPY", "MGf_DUP",
+ "MGf_LOCAL" and "VMG_UVAR" are also only exported on request. They are
+ all exported by the tags ':consts' and ':all'.
DEPENDENCIES
perl 5.7.3.
Carp (standard since perl 5), XSLoader (standard since perl 5.006).
+ Copy tests need Tie::Array (standard since perl 5.005) and Tie::Hash
+ (since 5.002).
+
+ Some uvar tests need Hash::Util::FieldHash (standard since perl
+ 5.009004).
+
Glob tests need Symbol (standard since perl 5.002).
SEE ALSO
perlguts and perlapi for internal information about magic.
+ perltie and overload for other ways of enhancing objects.
+
AUTHOR
Vincent Pit, "<perl at profvince.com>"
perldoc Variable::Magic
COPYRIGHT & LICENSE
- Copyright 2007 Vincent Pit, all rights reserved.
+ Copyright 2007-2008 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