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.
114 =head2 C<localize_delete $what, $key, $level>
116 Similiar to L</localize>, but for deleting objects or elements.
117 If C<$what> is a glob, it's equivalent to C<local *x;>, and C<$key> is ignored.
118 If C<$what> is a string beginning with C<'@'> or C<'%'>, it's equivalent to respectiveley C<local $a[$key]; delete $a[$key];> or C<local $h{$key}; delete $h{$key};>.
119 If C<$what> is a string beginning with C<'&'>, it's more or less of equivalent to C<undef &func;>, but actually more powerful as C<&func> won't even C<exists> anymore.
123 Returns the level that currently represents the highest scope.
127 The functions L</reap>, L</localize>, L</localize_elem>, L</localize_delete> and L</TOPLEVEL> are only exported on request, either individually or by the tags C<':funcs'> and C<':all'>.
131 use base qw/Exporter/;
135 funcs => [ qw/reap localize localize_elem localize_delete TOPLEVEL/ ],
137 our @EXPORT_OK = map { @$_ } values %EXPORT_TAGS;
138 $EXPORT_TAGS{'all'} = [ @EXPORT_OK ];
142 Be careful that local variables are restored in the reverse order in which they were localized.
143 Consider those examples:
147 reap sub { print $x } => 0;
155 reap sub { $x = 2 } => 0;
160 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>.
162 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.
163 This is an hopeless case because C<BEGIN> blocks are executed once while localizing constructs should do their job at each run.
167 L<XSLoader> (standard since perl 5.006).
171 L<Alias>, L<Hook::Scope>, L<Scope::Guard>, L<Guard>.
175 Vincent Pit, C<< <perl at profvince.com> >>, L<http://www.profvince.com>.
177 You can contact me by mail or on C<irc.perl.org> (vincent).
181 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.
185 You can find documentation for this module with the perldoc command.
189 Tests code coverage report is available at L<http://www.profvince.com/perl/cover/Scope-Upper>.
191 =head1 ACKNOWLEDGEMENTS
193 Inspired by Ricardo Signes.
195 =head1 COPYRIGHT & LICENSE
197 Copyright 2008 Vincent Pit, all rights reserved.
199 This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.
203 1; # End of Scope::Upper