+ variable. This function returns true on success, 0 when no magic
+ represented by $wiz could be found in the variable, and croaks if the
+ supplied wizard is invalid.
+
+ # Dispell now.
+ 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.
+
+ "MGf_DUP"
+ Evaluates to true iff the 'dup' magic is available.
+
+ "MGf_LOCAL"
+ 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.
+
+ "VMG_COMPAT_ARRAY_PUSH_NOLEN"
+ True for perls that don't call 'len' magic when you push an element in a
+ magical array. Starting from perl 5.11.0, this only refers to pushes in
+ non-void context and hence is false.
+
+ "VMG_COMPAT_ARRAY_PUSH_NOLEN_VOID"
+ True for perls that don't call 'len' magic when you push in void context
+ an element in a magical array.
+
+ "VMG_COMPAT_ARRAY_UNSHIFT_NOLEN_VOID"
+ True for perls that don't call 'len' magic when you unshift in void
+ context an element in a magical array.
+
+ "VMG_COMPAT_ARRAY_UNDEF_CLEAR"
+ True for perls that call 'clear' magic when undefining magical arrays.
+
+ "VMG_COMPAT_SCALAR_LENGTH_NOLEN"
+ True for perls that don't call 'len' magic when taking the "length" of a
+ magical scalar.
+
+ "VMG_PERL_PATCHLEVEL"
+ The perl patchlevel this module was built with, or 0 for non-debugging
+ perls.
+
+ "VMG_THREADSAFE"
+ True iff this module could have been built with thread-safety features
+ enabled.
+
+ "VMG_FORKSAFE"
+ True iff this module could have been built with fork-safety features
+ enabled. This will always be true except on Windows where it's false for
+ perl 5.10.0 and below .
+
+ "VMG_OP_INFO_NAME"
+ Value to pass with "op_info" to get the current op name in the magic
+ callbacks.
+
+ "VMG_OP_INFO_OBJECT"
+ Value to pass with "op_info" to get a "B::OP" object representing the
+ current op in the magic callbacks.
+
+COOKBOOK
+ Associate an object to any perl variable
+ This can be useful for passing user data through limited APIs.
+
+ {
+ package Magical::UserData;
+
+ use Variable::Magic qw/wizard cast getdata/;
+
+ my $wiz = wizard data => sub { \$_[1] };
+
+ sub ud (\[$@%*&]) : lvalue {
+ my ($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;
+ }
+ }
+
+ {
+ BEGIN { *ud = \&Magical::UserData::ud }
+
+ my $cb;
+ $cb = sub { print 'Hello, ', ud(&$cb), "!\n" };
+
+ ud(&$cb) = 'world';
+ $cb->(); # Hello, world!
+ }
+
+ Recursively cast magic on datastructures
+ "cast" can be called from any magical callback, and in particular from
+ "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 %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 "cast".
+
+PERL MAGIC HISTORY
+ 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.
+
+ * 5.8.9
+
+ *p28160* : Integration of *p25854* (see below).
+
+ *p32542* : Integration of *p31473* (see below).
+
+ * 5.9.3
+
+ *p25854* : 'len' magic is no longer called when pushing an element
+ into a magic array.
+
+ *p26569* : 'local' magic.
+
+ * 5.9.5
+
+ *p31064* : Meaningful 'uvar' magic.
+
+ *p31473* : 'clear' magic wasn't invoked when undefining an array.
+ The bug is fixed as of this version.
+
+ * 5.10.0
+
+ Since "PERL_MAGIC_uvar" is uppercased, "hv_magic_check()" triggers
+ 'copy' magic on hash stores for (non-tied) hashes that also have
+ 'uvar' magic.
+
+ * 5.11.x
+
+ *p32969* : 'len' magic is no longer invoked when calling "length"
+ with a magical scalar.
+
+ *p34908* : 'len' magic is no longer called when pushing / unshifting
+ an element into a magical array in void context. The "push" part was
+ already covered by *p25854*.
projects / perl / modules / Variable-Magic.git / blobdiff