NAME

Reflex::Trait::EmitsOnChange - Emit an event when an attribute's value changes.

VERSION

This document describes version 0.100, released on April 02, 2017.

SYNOPSIS

        # Not a complete program.  See examples eg-09-emitter-trait.pl
        # and eg-10-setup.pl for working examples.

        package Counter;
        use Moose;
        extends 'Reflex::Base';
        use Reflex::Trait::EmitsOnChange;

        emits count => (
                isa       => 'Int',
                default   => 0,
        );

An equivalent alternative:

        has count   => (
                traits    => ['Reflex::Trait::EmitsOnChange'],
                isa       => 'Int',
                is        => 'rw',
                default   => 0,
        );

DESCRIPTION

An attribute with the Reflex::Trait::EmitsOnChange trait emit an event on behalf of its object whenever its value changes. The event will be named after the attribute by default. It will be accompanied by a "value" parameter, the value of which is the attribute's new value at the time of the change.

In the SYNOPSIS example, changes to count() cause its Counter object to emit "count" events.

event

The "default" option can be used to override the default event emitted by the Reflex::Trait::EmitsOnChange trait. That default, by the way, is the name of the attribute.

setup

The "setup" option provides default constructor parameters for the attribute. In the above example, clock() will by default contain

        Reflex::Interval->new(interval => 1, auto_repeat => 1);

In other words, it will emit the Reflex::Interval event ("tick") once per second until destroyed.

Declarative Syntax

Reflex::Trait::EmitsOnChange exports a declarative emits() function, which acts almost identically to Moose's has() but with a couple convenient defaults: The EmitsOnChange trait is added, and the attribute is "rw" to allow changes.

CAVEATS

The "setup" option is a work-around for unfortunate default timing. It will be deprecated if default can be made to work instead.

BUGS AND LIMITATIONS

You can make new bug reports, and view existing ones, through the web interface at <http://rt.cpan.org/Public/Dist/Display.html?Name=Reflex>.

AUTHOR

Rocco Caputo <rcaputo@cpan.org>

COPYRIGHT AND LICENSE

This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.

AVAILABILITY

The latest version of this module is available from the Comprehensive Perl Archive Network (CPAN). Visit <http://www.perl.com/CPAN/> to find a CPAN site near you, or see <https://metacpan.org/module/Reflex/>.

DISCLAIMER OF WARRANTY

BECAUSE THIS SOFTWARE IS LICENSED FREE OF CHARGE, THERE IS NO WARRANTY FOR THE SOFTWARE, TO THE EXTENT PERMITTED BY APPLICABLE LAW. EXCEPT WHEN OTHERWISE STATED IN WRITING THE COPYRIGHT HOLDERS AND/OR OTHER PARTIES PROVIDE THE SOFTWARE "AS IS" WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE ENTIRE RISK AS TO THE QUALITY AND PERFORMANCE OF THE SOFTWARE IS WITH YOU. SHOULD THE SOFTWARE PROVE DEFECTIVE, YOU ASSUME THE COST OF ALL NECESSARY SERVICING, REPAIR, OR CORRECTION.

IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MAY MODIFY AND/OR REDISTRIBUTE THE SOFTWARE AS PERMITTED BY THE ABOVE LICENCE, BE LIABLE TO YOU FOR DAMAGES, INCLUDING ANY GENERAL, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE USE OR INABILITY TO USE THE SOFTWARE (INCLUDING BUT NOT LIMITED TO LOSS OF DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY YOU OR THIRD PARTIES OR A FAILURE OF THE SOFTWARE TO OPERATE WITH ANY OTHER SOFTWARE), EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES.