A simple message bus

icanboogie/message-bus provides a very simple message bus that can handle messages right away or push them in a queue. Implemented with a functional approach, it tries to be as flexible as possible: the message handler provider and the message pusher are defined with simple callables that you can implement with your favorite resolver and your favorite message queue.

Few components make most of it: The MessageBus interface defines a unique dispatch() method; ShouldBePushed should be implemented by messages that should be pushed in a queue rather than handled by the application; finally the class SimpleMessageBus is a simple implementation of MessageBus.

The following example demonstrates how to instantiate a message bus and dispatch a message:

<?php

namespace ICanBoogie\MessageBus;

/* @var MessageHandlerProvider|callable $message_handler_provider */
/* @var MessagePusher|callable $message_pusher */

$bus = new SimpleMessageBus($message_handler_provider, $message_pusher);

/* @var Message $message */

// The message is handled right away by an handler
$result = $bus->dispatch($message);

/* @var ShouldBePushed $message */

// The message is pushed to a queue
$bus->dispatch($message);

Message handler provider

The message handler provider is a callable with a signature similar to the MessageHandlerProvider interface, the package provides a simple message handler provider that only requires an array of key/value pairs, where key is a message class and value a message handler callable.

The following example demonstrates how to define a message handler provider with a selection of messages and their handlers:

<?php

use App\Application\Message;
use ICanBoogie\MessageBus\SimpleMessageHandlerProvider;

$message_handler_provider = new SimpleMessageHandlerProvider([

    Message\CreateArticle::class => function (Message\CreateArticle $message) {

        // create an article

    },

    Message\DeleteArticle::class => function (Message\DeleteArticle $message) {

        // delete an article

    },

]);

Of course, if you're using the icanboogie/service package, you can use service references instead of callables (well, technically, they are also callables):

<?php

use App\Application\Message;
use ICanBoogie\MessageBus\SimpleMessageHandlerProvider;

use function ICanBoogie\Service\ref;

$message_handler_provider = new SimpleMessageHandlerProvider([

    Message\CreateArticle::class => ref('handler.article.create'),
    Message\DeleteArticle::class => ref('handler.article.delete'),

]);

tl;dr

I reinvented the wheel by creating a message bus, but saved the universe in the process.