8 Scope::Upper - Act on upper scopes.
25 use Scope::Upper qw/reap localize localize_elem/;
27 sub desc { shift->{desc} }
32 # First localize $x so that it gets destroyed last
33 localize '$x' => bless({ desc => $desc }, __PACKAGE__) => 1;
37 my $x = do { no strict 'refs'; ${$pkg.'::x'} }; # Get the $x in the scope
38 print $x->desc . ": done\n";
41 localize_elem '%SIG', '__WARN__' => sub {
43 my $x = do { no strict 'refs'; ${$pkg.'::x'} }; # Get the $x in the scope
44 CORE::warn($x->desc . ': ' . join('', @_));
52 # $x is now a X object
53 warn 'what'; # warns "pie: what at ..."
55 } # "pie: done" is printed
59 This module lets you defer actions that will take place when the control flow returns into an upper scope.
60 Currently, you can hook an upper scope end, or localize variables and array/hash values in higher contexts.
68 XSLoader::load(__PACKAGE__, $VERSION);
71 =head2 C<reap $callback, $level>
73 Add a destructor that calls C<$callback> when the C<$level>-th upper scope ends, where C<0> corresponds to the current scope.
75 =head2 C<localize $what, $value, $level>
77 A C<local> delayed to the time of first return into the C<$level>-th upper scope.
84 A glob, in which case C<$value> can either be a glob or a reference.
85 L</localize> follows then the same syntax as C<local *x = $value>.
86 For example, if C<$value> is a scalar reference, then the C<SCALAR> slot of the glob will be set to C<$$value> - just like C<local *x = \1> sets C<$x> to C<1>.
90 A string beginning with a sigil, representing the symbol to localize and to assign to.
91 If the sigil is C<'$'>, L</localize> follows the same syntax as C<local $x = $value>, i.e. C<$value> isn't dereferenced.
94 localize '$x', \'foo' => 0;
96 will set C<$x> to a reference to the string C<'foo'>.
97 Other sigils (C<'@'>, C<'%'>, C<'&'> and C<'*'>) require C<$value> to be a reference of the corresponding type.
99 When the symbol is given by a string, it is resolved when the actual localization takes place and not when C<localize> is called.
102 sub tag { localize '$x', $_[0] => 1; }
104 will localize in the caller's namespace.
108 =head2 C<localize_elem $what, $key, $value, $level>
110 Similar to L</localize> but for array and hash elements.
111 If C<$what> is a glob, the slot to fill is determined from which type of reference C<$value> is ; otherwise it's inferred from the sigil.
112 C<$key> is either an array index or a hash key, depending of which kind of variable you localize.
116 Returns the level that currently represents the highest scope.
120 The functions L</reap>, L</localize>, L</localize_elem> and L</TOPLEVEL> are only exported on request, either individually or by the tags C<':funcs'> and C<':all'>.
124 use base qw/Exporter/;
128 funcs => [ qw/reap localize localize_elem TOPLEVEL/ ],
130 our @EXPORT_OK = map { @$_ } values %EXPORT_TAGS;
131 $EXPORT_TAGS{'all'} = [ @EXPORT_OK ];
135 Be careful that local variables are restored in the reverse order in which they were localized.
136 Consider those examples:
140 reap sub { print $x } => 0;
148 reap sub { $x = 2 } => 0;
153 The first case is "solved" by moving the C<local> before the C<reap>, and the second by using L</localize> instead of L</reap>.
155 L</reap>, L</localize> and L</localize_elem> effects can't cross C<BEGIN> blocks, hence calling those functions in C<import> is deemed to be useless.
156 This is an hopeless case because C<BEGIN> blocks are executed once while localizing constructs should do their job at each run.
160 L<XSLoader> (standard since perl 5.006).
164 L<Alias>, L<Hook::Scope>, L<Scope::Guard>, L<Guard>.
168 Vincent Pit, C<< <perl at profvince.com> >>, L<http://www.profvince.com>.
170 You can contact me by mail or on C<irc.perl.org> (vincent).
174 Please report any bugs or feature requests to C<bug-scope-upper at rt.cpan.org>, or through the web interface at L<http://rt.cpan.org/NoAuth/ReportBug.html?Queue=Scope-Upper>. I will be notified, and then you'll automatically be notified of progress on your bug as I make changes.
178 You can find documentation for this module with the perldoc command.
182 Tests code coverage report is available at L<http://www.profvince.com/perl/cover/Scope-Upper>.
184 =head1 ACKNOWLEDGEMENTS
186 Inspired by Ricardo Signes.
188 =head1 COPYRIGHT & LICENSE
190 Copyright 2008 Vincent Pit, all rights reserved.
192 This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.
196 1; # End of Scope::Upper