Events subsystem

[davidnewcomb]

Each forum thread is related to one entity on my site. So I am creating threads, merging and deleting them as I create update and delete my own entities. In order for the forums to "talk" back to the main application, I had to add an events system.

src/events/EventService - easy way of sending events.
src/events/PodiumEvent - event names.
src/events/PodiumThreadEvent - event object for events about threads.

I have triggered thread events inside Thread and Post. To keep it simple, I trigger a thread update event whenever anything happens to the posts of that thread.

Using it is easy:

main.php

'forum' => [
        'class' => 'bizley\podium\Podium',
        // Events
        'on '. PodiumEvent::THREAD_CREATED => ['app\components\PodiumListener', 'handler'],
        'on '. PodiumEvent::THREAD_UPDATED => ['app\components\PodiumListener', 'handler'],
        'on '. PodiumEvent::THREAD_DELETED => ['app\components\PodiumListener', 'handler'],

PodiumListener.php

<?php
namespace app\components;

use common\models\MyEntity;

class PodiumListener {

	public static function handler($event) {
		$link = $event->thread->name;
		$p = MyEntity::findOne(["link" => $link]);
		if ($p) {
			$p->updated_at = time();
			$p->save();
		}
		return true;
	}
}

I just needed to have my entity's last modified time linked with the thread, but after doing it I can see loads of other possibilities with other events. One that sprang to mind was catching each Post create/update, parsing the URLs out of it and filing them somewhere else.

I can see it being useful to run actions when threads or posts are created, etc.
Like I said, I've kept it simple to see what the reaction is like.

The only thing worth mentioning is that I wasn't sure if you wanted to include the event triggering inside the thread create/update/delete transaction. I decided to place them just outside because I didn't want the transaction to rollback for an event sending failure. But it's up to you really!

[bizley]

I'm in the middle of splitting Podium into API engine and module implementing it and events are there already ;) So good idea in general. Let me keep this PR for reference until the new version is out.