2 Scope::Upper - Act on upper scopes.
10 use Scope::Upper qw/reap localize localize_elem/;
12 sub desc { shift->{desc} }
17 # First localize $x so that it gets destroyed last
18 localize '$x' => bless({ desc => $desc }, __PACKAGE__) => 1;
22 my $x = do { no strict 'refs'; ${$pkg.'::x'} }; # Get the $x in the scope
23 print $x->desc . ": done\n";
26 localize_elem '%SIG', '__WARN__' => sub {
28 my $x = do { no strict 'refs'; ${$pkg.'::x'} }; # Get the $x in the scope
29 CORE::warn($x->desc . ': ' . join('', @_));
37 # $x is now a X object
38 warn 'what'; # warns "pie: what at ..."
40 } # "pie: done" is printed
43 This module lets you defer actions that will take place when the control
44 flow returns into an upper scope. Currently, you can hook an upper scope
45 end, or localize variables and array/hash values in higher contexts.
48 "reap $callback, $level"
49 Add a destructor that calls $callback when the $level-th upper scope
50 ends, where 0 corresponds to the current scope.
52 "localize $what, $value, $level"
53 A "local" delayed to the time of first return into the $level-th upper
56 * A glob, in which case $value can either be a glob or a reference.
57 "localize" follows then the same syntax as "local *x = $value". For
58 example, if $value is a scalar reference, then the "SCALAR" slot of
59 the glob will be set to $$value - just like "local *x = \1" sets $x
62 * A string beginning with a sigil, representing the symbol to localize
63 and to assign to. If the sigil is '$', "localize" follows the same
64 syntax as "local $x = $value", i.e. $value isn't dereferenced. For
67 localize '$x', \'foo' => 0;
69 will set $x to a reference to the string 'foo'. Other sigils ('@',
70 '%', '&' and '*') require $value to be a reference of the
73 When the symbol is given by a string, it is resolved when the actual
74 localization takes place and not when "localize" is called. This
77 sub tag { localize '$x', $_[0] => 1; }
79 will localize in the caller's namespace.
81 "localize_elem $what, $key, $value, $level"
82 Similar to "localize" but for array and hash elements. If $what is a
83 glob, the slot to fill is determined from which type of reference $value
84 is ; otherwise it's inferred from the sigil. $key is either an array
85 index or a hash key, depending of which kind of variable you localize.
88 Returns the level that currently represents the highest scope.
91 The functions "reap", "localize", "localize_elem" and "TOPLEVEL" are
92 only exported on request, either individually or by the tags ':funcs'
96 Be careful that local variables are restored in the reverse order in
97 which they were localized. Consider those examples:
101 reap sub { print $x } => 0;
109 reap sub { $x = 2 } => 0;
114 The first case is "solved" by moving the "local" before the "reap", and
115 the second by using "localize" instead of "reap".
117 "reap", "localize" and "localize_elem" effects can't cross "BEGIN"
118 blocks, hence calling those functions in "import" is deemed to be
119 useless. This is an hopeless case because "BEGIN" blocks are executed
120 once while localizing constructs should do their job at each run.
123 XSLoader (standard since perl 5.006).
126 Alias, Hook::Scope, Scope::Guard, Guard.
129 Vincent Pit, "<perl at profvince.com>", <http://www.profvince.com>.
131 You can contact me by mail or on "irc.perl.org" (vincent).
134 Please report any bugs or feature requests to "bug-scope-upper at
135 rt.cpan.org", or through the web interface at
136 <http://rt.cpan.org/NoAuth/ReportBug.html?Queue=Scope-Upper>. I will be
137 notified, and then you'll automatically be notified of progress on your
138 bug as I make changes.
141 You can find documentation for this module with the perldoc command.
145 Tests code coverage report is available at
146 <http://www.profvince.com/perl/cover/Scope-Upper>.
149 Inspired by Ricardo Signes.
152 Copyright 2008 Vincent Pit, all rights reserved.
154 This program is free software; you can redistribute it and/or modify it
155 under the same terms as Perl itself.