Role::EventEmitter(3pm)

Usage

  package Channel;
  use Moo;
  with 'Role::EventEmitter';
  # Emit events
  sub send_message {
    my $self = shift;
    $self->emit(message => @_);
  }
  package main;
  # Subscribe to events
  my $channel_a = Channel->new;
  $channel_a->on(message => sub {
    my ($channel, $text) = @_;
    say "Received message: $text";
  });
  $channel_a->send_message('All is well');

Overview

Role::EventEmitter is a simple Role::Tiny role for event emitting objects based on Mojo::EventEmitter. This role can be applied to any hash-based object class such as those created with Class::Tiny, Moo, or Moose.

Events

Role::EventEmitter can emit the following events.

error

  $e->on(error => sub {
    my ($e, $err) = @_;
    ...
  });

This is a special event for errors, it will not be emitted directly by this role but is fatal if unhandled.

  $e->on(error => sub {
    my ($e, $err) = @_;
    say "This looks bad: $err";
  });

Methods

Role::EventEmitter composes the following methods.

catch

  $e = $e->catch(sub {...});

Subscribe to "error" event.

  # Longer version
  $e->on(error => sub {...});

emit

  $e = $e->emit('foo');
  $e = $e->emit('foo', 123);

Emit event.

has_subscribers

  my $bool = $e->has_subscribers('foo');

Check if event has subscribers.

on

  my $cb = $e->on(foo => sub {...});

Subscribe to event.

  $e->on(foo => sub {
    my ($e, @args) = @_;
    ...
  });

once

  my $cb = $e->once(foo => sub {...});

Subscribe to event and unsubscribe again after it has been emitted once.

  $e->once(foo => sub {
    my ($e, @args) = @_;
    ...
  });

once_f

  my $f = $e->once_f('foo');

Subscribe to event as in "once", returning a Future that will be marked complete after it has been emitted once. Requires Future to be installed.

  my $f = $e->once_f('foo')->on_done(sub {
    my ($e, @args) = @_;
    ...
  });

To unsubscribe the returned Future early, cancel it.

  $f->cancel;

subscribers

  my $subscribers = $e->subscribers('foo');

All subscribers for event.

  # Unsubscribe last subscriber
  $e->unsubscribe(foo => $e->subscribers('foo')->[-1]);
  # Change order of subscribers
  @{$e->subscribers('foo')} = reverse @{$e->subscribers('foo')};

unsubscribe

  $e = $e->unsubscribe('foo');
  $e = $e->unsubscribe(foo => $cb);

Unsubscribe from event. Related Futures will also be cancelled.

Debugging

You can set the "ROLE_EVENTEMITTER_DEBUG" environment variable to get some advanced diagnostics information printed to "STDERR".

  ROLE_EVENTEMITTER_DEBUG=1

Copyright and license

This is free software, licensed under:

  The Artistic License 2.0 (GPL Compatible)

Releases

Unchanged in 2 releases since Debian 12 (Bookworm).

12–13