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package Scope::Guard;
use strict;
use warnings;
use Carp qw(confess);
use Exporter ();
our @ISA = qw(Exporter);
our @EXPORT_OK = qw(guard scope_guard);
our $VERSION = '0.21';
sub new {
confess "Can't create a Scope::Guard in void context" unless (defined wantarray);
my $class = shift;
my $handler = shift() || die 'Scope::Guard::new: no handler supplied';
my $ref = ref $handler || '';
die "Scope::Guard::new: invalid handler - expected CODE ref, got: '$ref'"
unless ref($handler) eq 'CODE';
bless [ 0, $handler ], ref $class || $class;
}
sub dismiss {
my $self = shift;
my $dismiss = @_ ? shift : 1;
$self->[0] = $dismiss;
}
sub guard(&) { __PACKAGE__->new(shift) }
sub scope_guard($) { __PACKAGE__->new(shift) }
sub DESTROY {
my $self = shift;
my ($dismiss, $handler) = @$self;
$handler->() unless ($dismiss);
}
1;
__END__
=pod
=head1 NAME
Scope::Guard - lexically-scoped resource management
=head1 SYNOPSIS
my $guard = guard { ... };
# or
my $guard = scope_guard \&handler;
# or
my $guard = Scope::Guard->new(sub { ... });
$guard->dismiss(); # disable the handler
=head1 DESCRIPTION
This module provides a convenient way to perform cleanup or other forms of resource
management at the end of a scope. It is particularly useful when dealing with exceptions:
the C<Scope::Guard> constructor takes a reference to a subroutine that is guaranteed to
be called even if the thread of execution is aborted prematurely. This effectively allows
lexically-scoped "promises" to be made that are automatically honoured by perl's garbage
collector.
For more information, see: L<http://www.drdobbs.com/cpp/184403758>
=head1 METHODS
=head2 new
my $guard = Scope::Guard->new(sub { ... });
# or
my $guard = Scope::Guard->new(\&handler);
The C<new> method creates a new C<Scope::Guard> object which calls the supplied handler when its C<DESTROY> method is
called, typically at the end of the scope.
=head2 dismiss
$guard->dismiss();
# or
$guard->dismiss(1);
C<dismiss> detaches the handler from the C<Scope::Guard> object. This revokes the "promise" to call the
handler when the object is destroyed.
The handler can be re-enabled by calling:
$guard->dismiss(0);
=head1 EXPORTS
=head2 guard
C<guard> takes a block and returns a new C<Scope::Guard> object. It can be used
as a shorthand for:
Scope::Guard->new(...)
e.g.
my $guard = guard { ... };
Note: calling C<guard> anonymously, i.e. in void context, will raise an exception.
This is because anonymous guards are destroyed B<immediately>
(rather than at the end of the scope), which is unlikely to be the desired behaviour.
=head2 scope_guard
C<scope_guard> is the same as C<guard>, but it takes a code ref rather than a block.
e.g.
my $guard = scope_guard \&handler;
or:
my $guard = scope_guard sub { ... };
or:
my $guard = scope_guard $handler;
As with C<guard>, calling C<scope_guard> in void context will raise an exception.
=head1 VERSION
0.21
=head1 SEE ALSO
=over
=item * L<B::Hooks::EndOfScope|B::Hooks::EndOfScope>
=item * L<End|End>
=item * L<Guard|Guard>
=item * L<Hook::Scope|Hook::Scope>
=item * L<Object::Destroyer|Object::Destroyer>
=item * L<Perl::AtEndOfScope|Perl::AtEndOfScope>
=item * L<ReleaseAction|ReleaseAction>
=item * L<Scope::local_OnExit|Scope::local_OnExit>
=item * L<Scope::OnExit|Scope::OnExit>
=item * L<Sub::ScopeFinalizer|Sub::ScopeFinalizer>
=item * L<Value::Canary|Value::Canary>
=back
=head1 AUTHOR
chocolateboy <chocolate@cpan.org>
=head1 COPYRIGHT
Copyright (c) 2005-2015, chocolateboy.
This module is free software. It may be used, redistributed and/or modified under the same terms
as Perl itself.
=cut