NAME

Async::Event::Interval - Extremely simple timed asynchronous events

SYNOPSIS

A simple event. Multiple events can be simultaneously used. For an example using an event that can share data with the main application, examples of how to handle event crashes, and how to send parameters to your event callback, see "EXAMPLES".

    use Async::Event::Interval;

    my $event = Async::Event::Interval->new(
        1.5, 
        \&callback
    );

    $event->start;

    for (1..10){
        print "$_: in main loop\n";

        $event->stop if $_ == 3;
        $event->start if $_ == 7;

        if ($event->status){
            print "event is running\n";
        }

        if ($event->status == -1){
            print "event has crashed... restarting it\n";
            $event->restart;
        }

        sleep 1;
    }

    sub callback {
        print "timed event callback\n";
    }

DESCRIPTION

Very basic implementation of asynchronous events that are triggered by a timed interval. If no time is specified, we'll run the event only once.

Variables are not shared between the main application and the event. To do that, you'll need to use some form of memory sharing, such as IPC::Shareable. See "EXAMPLES" for an example. At this time, there is no real parameter passing or ability to return values. As I said... basic.

Each event is simply a separate forked process, which runs in a while loop.

METHODS

new($delay, $callback)

Returns a new Async::Event::Interval object. Does not create the event. Use start for that.

Parameters:

    $delay

Mandatory: The interval on which to trigger your event callback, in seconds. Represent partial seconds as a floating point number. If zero is specified, we'll simply run the event once and stop.

    $callback

Mandatory: A reference to a subroutine that will be called every time the interval expires.

start

Starts the event timer. Each time the interval is reached, the event callback is executed.

stop

Stops the event from being executed.

restart

Alias for start(). Re-starts a stop()ped event.

status

Returns the event's process ID (true) if it is running, 0 (false) if it isn't, and -1 if the event has crashed.

waiting

Returns true if the event is dormant and is ready for a start() or restart command. Returns false if the event is already running.

EXAMPLES

Run Once

Send in an interval of zero (0) to have your event run a single time. Call start() repeatedly for numerous runs.

    use Async::Event::Interval

    my $event = Async::Event::Interval->new(0, sub {print "hey\n";});

    $event->start;

    # Do stuff, then run the event again if it's done its previous task

    $event->start if $event->waiting;

Event Parameters

You can send in a list of parameters to the event callback. Changing these within the main program will have no effect on the values sent into the event itself.

    use Async::Event::Interval

    my @params = qw(1 2 3);

    my $event = Async::Event::Interval->new(
        1,
        \&callback,
        @params
    );

    sub callback {
        my ($one, $two, $three) = @_;
        print "$one, $two, $three\n";
    }

Shared Data

A timed event where the event callback shares a scalar variable with the main program.

    use Async::Event::Interval;
    use IPC::Shareable;

    tie my $scalar, 'IPC::Shareable', 'KEY', {create => 1, destroy => 1};
    $scalar = "hello";

    my $event
        = Async::Event::Interval->new(10, \&callback);

    sub callback {
        $scalar = "hello, world!";
    }

Event crash: Restart event

    use warnings;
    use strict;
    use feature 'say';

    use Async::Event::Interval;

    my $event = Async::Event::Interval->new(
        2,
        sub {
            kill 9, $$;
        },
    );

    $event->start;

    sleep 1; # do stuff

    if ($event->status == -1){
        say "event crashed, restarting";
        $event->restart;
    }

Event crash: End program

    use warnings;
    use strict;
    use feature 'say';

    use Async::Event::Interval;

    my $event = Async::Event::Interval->new(
        2,
        sub {
            kill 9, $$;
        },
    );

    $event->start;

    sleep 1; # do stuff

    if ($event->status == -1){
        say "event crashed, can't continue...";
        exit;
    }

AUTHOR

Steve Bertrand, <steveb at cpan.org>

LICENSE AND COPYRIGHT

Copyright 2021 Steve Bertrand.

This program is free software; you can redistribute it and/or modify it under the terms of either: the GNU General Public License as published by the Free Software Foundation; or the Artistic License.

See http://dev.perl.org/licenses/ for more information.

cpanm Async::Event::Interval

perl -MCPAN -e shell
install Async::Event::Interval