Mojo::EventEmitter

Section: User Contributed Perl Documentation (3)
Updated: 2018-11-22
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NAME

Mojo::EventEmitter - Event emitter base class

SYNOPSIS

  package Cat;
  use Mojo::Base 'Mojo::EventEmitter';

  # Emit events
  sub poke {
    my $self = shift;
    $self->emit(roar => 3);
  }

  package main;

  # Subscribe to events
  my $tiger = Cat->new;
  $tiger->on(roar => sub {
    my ($tiger, $times) = @_;
    say 'RAWR!' for 1 .. $times;
  });
  $tiger->poke;

DESCRIPTION

Mojo::EventEmitter is a simple base class for event emitting objects.

EVENTS

Mojo::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 class, but is fatal if unhandled. Subclasses may choose to emit it, but are not required to do so.

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

METHODS

Mojo::EventEmitter inherits all methods from Mojo::Base and implements the following new ones.

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) = @_;
    ...
  });

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.

DEBUGGING

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

  MOJO_EVENTEMITTER_DEBUG=1