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Event::Join(3) User Contributed Perl Documentation Event::Join(3)

Event::Join - join multiple "events" into one

    use Event::Join;
    my $joiner = Event::Join->new(
        on_completion => sub {
            my $events = shift;
            say 'Child exited with status '. $events->{child_done};
        events => [qw/stdout_closed child_done/],
    watch_fh $stdout, on_eof  => sub { $joiner->send_event('stdout_closed') };
    watch_child $pid, on_exit => sub { $joiner->send_event('child_done', $_[0]) };

When writing event-based programs, you often want to wait for a number of events to occur, and then do something. This module allows you to do that without blocking. It simply acts as a receiver for a number of events, and then calls a callback when all events have occurred.
Note that although I mainly use this for "real" event-based programming, the technique is rather versatile. A config file parser could be implemented like this:
   my $parsed_doc;
   my $parser_state = Event::Join->new(
       events        => [qw/username password machine_name/],
       on_completion => sub { $parsed_doc = shift },
   while(!$parsed_doc && (my $line = <$fh>)){
       chomp $line;
       my ($k, $v) = split /:/, $line;
       $parser_state->send_event($k, $v);
   say 'Username is '. $parsed_doc->{username};

Create an instance. Needs to be passed "events", an arrayref of valid event names, and "on_completion", a coderef to call after all events have been received. This coderef is passed a hashref of events and their values, and will only ever be called once (or not at all, if the events never arrive).

Send an event. $event_name is required, and must be an event that was passed to the constructor. An exception will be thrown if the name is not valid.
$event_value is optional; is is the value that goes into the hash to be passed to the callback. It can be true or false -- its value does not affect whether or not the completino callback is called.
Finally, an exception is thrown if an event is sent more than once.

Returns true if the event has been sent, false otherwise. Note that the true value is not the value that was passed to "send_event", it is just an arbitrary non-false value.

Returns a coderef that sends $event_name when run. The first argument to the coderef will become the second argument to "send_event".

Is the module totally broken? Patch my repository at:

Jonathan Rockway "<>"

Copyright (c) 2009 Jonathan Rockway.
This module is Free Software. You may distribute it under the same terms as Perl itself.
2011-02-25 perl v5.28.1

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