NAME

MooX::EventHandler - Use Moo modules with event handlers.

SYNOPSIS

package Daisy;
use Moo;
use MooX::EventHandler;

has_event 'on_abattoir';

sub on_abattoir { die } # Cannot be replaced by users

has_event 'on_new_grass' => builder => sub { sub { # Yes, two
    my $self = shift;
    $self->eat();
}};

has_event 'on_bull' => builder => 'make_calf';

sub make_calf { sub { # Two again
    Daisy->new();
}}

DESCRIPTION

Exports a function has_event which creates an attribute with settings useful for writing event-driven code.

Specifically:

• Event attributes are lazy by default.

• The attribute is named _${event}_event so that $event() calls the event handler rather than returning the coderef which implements it. The init_arg remains $event and the default builder _build_$event.

• required now means that the default event handler will die, not that a handler must be passed to the constructor.

• (Optionally) Another attribute is added to the class which returns a listref of this object's event.

BUGS

Tracked events do not work correctly with inheritence or roles.

Double-layered subs are ugly.

This was written primarily for use with IO::Async and has not been tested with other event libraries.

Overriding/updating attribute options in subclasses has no explicit support and probably doesn't work.

There are no tests.

EVENT ATTRIBUTES

Event attributes are simply regular Moo attributes with defaults useful for writing event-driven code and as such can be treated like any other attribute, but see "BUGS".

There are 3 different ways to assign handlers to an event.

A lazy builder.

A coderef can be returned from an event attribute's builder or default in the usual way.

Passed to the constructor.

Coderefs can be passed to the constructor with the name of the event just like any other attribute.

Directly in the object.

The event handler can be installed as a regular method in the class. This overrides the ability to pass event handlers to the constructor.

EVENT TRACKING

If MooX::EventHandler is imported with the -tracked option and the name of an attribute, that attribute is created and set up to return a list of all of the object's events. This feature is buggy and does not work properly with inheritence.

package Foo;
use Moo;
use MooX::EventHandler -tracked => 'all_events';
has_event 'on_foo';
has_event 'on_bar';

# Foo->new->all_events will now return ['on_foo', 'on_bar'];

SEE ALSO

Moo

AUTHOR

Matthew King <chohag@jtan.com>