Yii2: Can I attach events from outside the model class? - php

Question

I am currently writing a class that caches model data for a select field.
Now obviously, if any model that is affecting this select field gets inserted, updated or deleted, the cache must be refreshed.
To handle this, I'd like to use the model events of Yii2. For example, if EVENT_AFTER_INSERT is triggered in the model Album, I want to execute the code to refresh the cache of the album select data.
Now I could do this the classical way and add an event to the model Album like this:
class Album extends ActiveRecord {
public function init(){
$this->on(self::EVENT_AFTER_INSERT, [$this, 'refresh_cache']);
$this->on(self::EVENT_AFTER_UPDATE, [$this, 'refresh_cache']);
$this->on(self::EVENT_AFTER_DELETE, [$this, 'refresh_cache']);
}
// ...
}
That would work, yes. Problem is, I'd need to include this code in any model I'd like to create a select field from at any point of development. It's not such a big deal, but you can easily forget it while coding and if the behavior needs to change at some point, you need to update a whole bunch of models.
Now here is my question: Is there any possibility to add events to a model from another component? My idea would be to create a component, that knows about all used select data caches and adds the necessary model events accordingly. any idea how to achieve this or something similar?

Answer 1

you just need create a behaviour and attach it to your various models. see the basic guide and speciffically the Behavior::events() use case
so i went ahead and wrote an example
class RefreshCacheBehavior extends \yii\base\Behavior
{
public function events() {
return [
\yii\db\ActiveRecord::EVENT_AFTER_INSERT => 'refreshCache',
\yii\db\ActiveRecord::EVENT_AFTER_UPDATE => 'refreshCache',
\yii\db\ActiveRecord::EVENT_AFTER_DELETE => 'refreshCache',
];
}
/**
* event handler
* #param \yii\base\Event $event
*/
public function refreshCache($event) {
// model that triggered the event will be $this->owner
// do things with Yii::$app->cache
}
}
class Album extends ActiveRecord {
public function behaviors() {
return [
['class' => RefreshCacheBehavior::className()],
];
}
// ...
}

Answer 2

Is there any possibility to add events to a model from another component?
Yes! You can use class level event handlers. The line of code below shows how to do that.
Event::on(ActiveRecord::className(), ActiveRecord::EVENT_AFTER_INSERT, function ($event) {
Yii::debug(get_class($event->sender) . ' is inserted');
});
You can use same code in your init method and bind it to your class method instead of that closure.
I would create a class implementing BootstrapInterface and add it to config. Then I would handle those class level events there!
Do yourself a favour and read about events in the Guide as well as the API Documentation

Answer 3

on() is a public method, so you can always attach event to already instantiated object. This may be useful if you're using some kind of factory do build your objects:
public function createModel($id) {
$model = Album::findOne($id);
if ($model === null) {
// some magic
}
$model->on(Album::EVENT_AFTER_INSERT, [$this, 'refresh_cache']);
$model->on(Album::EVENT_AFTER_UPDATE, [$this, 'refresh_cache']);
$model->on(Album::EVENT_AFTER_DELETE, [$this, 'refresh_cache']);
return $model;
}