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.\" ========================================================================
.\"
.IX Title "Mojo::EventEmitter 3pm"
.TH Mojo::EventEmitter 3pm "2017-01-24" "perl v5.24.1" "User Contributed Perl Documentation"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
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.nh
.SH "NAME"
Mojo::EventEmitter \- Event emitter base class
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 2
\&  package Cat;
\&  use Mojo::Base \*(AqMojo::EventEmitter\*(Aq;
\&
\&  # 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 \*(AqRAWR!\*(Aq for 1 .. $times;
\&  });
\&  $tiger\->poke;
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
Mojo::EventEmitter is a simple base class for event emitting objects.
.SH "EVENTS"
.IX Header "EVENTS"
Mojo::EventEmitter can emit the following events.
.SS "error"
.IX Subsection "error"
.Vb 4
\&  $e\->on(error => sub {
\&    my ($e, $err) = @_;
\&    ...
\&  });
.Ve
.PP
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.
.PP
.Vb 4
\&  $e\->on(error => sub {
\&    my ($e, $err) = @_;
\&    say "This looks bad: $err";
\&  });
.Ve
.SH "METHODS"
.IX Header "METHODS"
Mojo::EventEmitter inherits all methods from Mojo::Base and implements
the following new ones.
.SS "catch"
.IX Subsection "catch"
.Vb 1
\&  $e = $e\->catch(sub {...});
.Ve
.PP
Subscribe to \*(L"error\*(R" event.
.PP
.Vb 2
\&  # Longer version
\&  $e\->on(error => sub {...});
.Ve
.SS "emit"
.IX Subsection "emit"
.Vb 2
\&  $e = $e\->emit(\*(Aqfoo\*(Aq);
\&  $e = $e\->emit(\*(Aqfoo\*(Aq, 123);
.Ve
.PP
Emit event.
.SS "has_subscribers"
.IX Subsection "has_subscribers"
.Vb 1
\&  my $bool = $e\->has_subscribers(\*(Aqfoo\*(Aq);
.Ve
.PP
Check if event has subscribers.
.SS "on"
.IX Subsection "on"
.Vb 1
\&  my $cb = $e\->on(foo => sub {...});
.Ve
.PP
Subscribe to event.
.PP
.Vb 4
\&  $e\->on(foo => sub {
\&    my ($e, @args) = @_;
\&    ...
\&  });
.Ve
.SS "once"
.IX Subsection "once"
.Vb 1
\&  my $cb = $e\->once(foo => sub {...});
.Ve
.PP
Subscribe to event and unsubscribe again after it has been emitted once.
.PP
.Vb 4
\&  $e\->once(foo => sub {
\&    my ($e, @args) = @_;
\&    ...
\&  });
.Ve
.SS "subscribers"
.IX Subsection "subscribers"
.Vb 1
\&  my $subscribers = $e\->subscribers(\*(Aqfoo\*(Aq);
.Ve
.PP
All subscribers for event.
.PP
.Vb 2
\&  # Unsubscribe last subscriber
\&  $e\->unsubscribe(foo => $e\->subscribers(\*(Aqfoo\*(Aq)\->[\-1]);
\&
\&  # Change order of subscribers
\&  @{$e\->subscribers(\*(Aqfoo\*(Aq)} = reverse @{$e\->subscribers(\*(Aqfoo\*(Aq)};
.Ve
.SS "unsubscribe"
.IX Subsection "unsubscribe"
.Vb 2
\&  $e = $e\->unsubscribe(\*(Aqfoo\*(Aq);
\&  $e = $e\->unsubscribe(foo => $cb);
.Ve
.PP
Unsubscribe from event.
.SH "DEBUGGING"
.IX Header "DEBUGGING"
You can set the \f(CW\*(C`MOJO_EVENTEMITTER_DEBUG\*(C'\fR environment variable to get some
advanced diagnostics information printed to \f(CW\*(C`STDERR\*(C'\fR.
.PP
.Vb 1
\&  MOJO_EVENTEMITTER_DEBUG=1
.Ve
.SH "SEE ALSO"
.IX Header "SEE ALSO"
Mojolicious, Mojolicious::Guides, <http://mojolicious.org>.