NAME

       Mojo::EventEmitter - Event emitter base class

SYNOPSIS

         package Cat;
         use Mojo::Base 'Mojo::EventEmitter', -signatures;

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

         package main;

         # Subscribe to events
         my $tiger = Cat->new;
         $tiger->on(roar => sub ($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
         $e->on(error => sub ($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.

         $e->on(error => sub ($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.

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

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

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

         $e->once(foo => sub ($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

SEE ALSO

       Mojolicious, Mojolicious::Guides, <https://mojolicious.org>.