Models and Event Handlers.

Yii 1.1 General Discussion
1

Say i have a model for a contest table, and i have a property called "name" that defines the name of the contest.

Now, i want to be able to attach distinct events for this property, for example, before i echo it in frontend i want to CHtml::encode() it, or say i have a component that i plug in and that component has a method which transforms the name in uppercase or makes it bold or similar behavior(if you are familiar with wordpress, think at add_filters() functionality), basically i want to let an open door to change this property before i retrieve it.

Right now i have something like:




<?php

//model class

class Contest extends CActiveRecord

{

    

    public function onBeforeGetName($event)

    {

        $this->raiseEvent('onBeforeGetName', $event);

    }

    

    public function beforeGetName()

    {

        if($this->hasEventHandler('onBeforeGetName'))

        {

            $event=new CModelEvent($this);

            $this->onBeforeGetName($event);

            return $event->isValid;

        }

        else

            return true;

    }

    

    public function getName()

    {

        $this->beforeGetName();

        

        return $this->name;

    }


    [...]


    [...]

}

So i added an event handler to be executed right before i request the name property of my model

My controller looks like:




<?php

class SiteController extends CmsFrontendController

{

    private $model;

    

    public function actionTest()

    {

        $this->model=Contest::model()->findByPk(20);

        $this->model->attachEventHandler('onBeforeGetName', array($this, 'upperName'));

        $this->model->getEventHandlers('onBeforeGetName')->add(array($this, 'boldName'));

        echo $this->model->getName();

    }

    

    public function upperName()

    {

        $this->model->name=strtoupper($this->model->name);

    }

    

    public function boldName()

    {

        $this->model->name='<b>'.$this->model->name.'</b>';

    }

    [...]

   

    [...]

}

All this seems correct to you ?

I mean, it looks a bit messy from my point of view, but once again, as i stated, i don’t fully understand the events mechanism in yii.

LE:

But what if i need to attach this event handler to a component, what do i do then , because i don’t have access to the model instance anymore ($this->model from the controller in my case)

2

I’m confused why you would do this using events and not just have the appropriate CHtml method calls in the views.

3

Eh, the idea is that during runtime, on various points of my script, i want to be able to attach some "hooks" to alter the model properties in various ways.

4

what about a behaviour?

http://blog.mbischof.de/ein-anrede-behavior

5

Hi there mbi and thx for the reply.

Yes, i am looking for something like this, basically your example is perfect, the only thing is that in your model you define the behaviors like:




public function behaviors()

{

    return array(

        'salutation' => array(

            'class' => 'ext.behaviors.CSalutationBehavior'

        )

    );

}

But in my case, i would like to attach them dinamically from various components/extensions, that’s why i thought that events are more suited for this situation.

But i might went wrong with this idea from the start, so i will repeat that what i really want to accomplish is something in wordpress filters style.

Say i have a component that has a method that makes the font bold, and another one that makes it upper case, let’s call these methods “filters”.

After i load the model in my controller, i want to check what "filters" should i apply for that model property and if it is the case, pass the property of the model through those filters.

If you take a look at my first example, and test it, you’ll see that it does just that, but at a controller level, not in a component.

Hope i was clear enough, if not… well, i give up :)

6

Well, i have some new findings.

Seems like i was looking for behaviors but wasn’t aware of that.

Anyway, i also found a neat solution to change the model properties by attaching events.

Here is the example:




<?php

//CONTROLLER METHOD: 

    public function actionIndex()

    {

        Yii::import('application.modules.contest.components.*');

        Yii::import('application.modules.contest.models.*');


        $contest=Contest::model()->findByPk(20);

        

        $contest->attachEventHandler('onBeforeGetName', array(CXTest::model(&$contest), 'getBoldName'));

        $contest->attachEventHandler('onBeforeGetName', array(CXTest::model(&$contest), 'getUpperName'));

        

        echo $contest->getName();

    }




?>







<?php

//MODEL EVENT HANDLERS


    public function onBeforeGetName($event)

    {

        $this->raiseEvent('onBeforeGetName', $event);

    }

    

    public function beforeGetName()

    {

        if($this->hasEventHandler('onBeforeGetName'))

        {

            $event=new CModelEvent($this);

            $this->onBeforeGetName($event);

            return $event->isValid;

        }

        else

            return true;

    }

    

    public function getName()

    {

        $this->beforeGetName();

        

        return $this->name;

    }


?>







<?php 

//Component which suppose to alter the content.

class CXTest

{

    public $model;

    private static $class_call=false;

    private static $_models=array();


    public static function model($model)

    {

        self::$class_call=true;

        $class=get_class($model);

        if(empty(self::$_models[$class]))

        {

            $_model=new self;

            $_model->model=$model;

            self::$_models[$class]=$_model;

        }

        self::$class_call=false;

        return self::$_models[$class];

    }


    public function __construct()

    {

        if($this->model===null&&self::$class_call===false)

            throw new CException(Yii::t('app', 'Please instantiate the model first'));

    }

    

    public function setName($str)

    {

        $this->model->name=$str;

    }

    

    public function getName()

    {

        return $this->model->name;

    }


    public function getBoldName()

    {

        $this->setName('<b>'.$this->model->name.'</b>');

    }

    

    public function getUpperName()

    {

        $this->setName(strtoupper($this->model->name));

    }


}

?>

As i said, i am aware that this could be accomplished via behaviors as well, but this demonstrates it can be done via events too.

Any thoughts on this ?

7

Hah thanks to mbi’s blog post: http://blog.mbischof.de/yiiframework-events i discovered the “sender” property so right now, the CXTest becomes :




<?php

class CXTest extends CApplicationComponent

{


    public function getBoldName($event)

    {

        $event->sender->name = '<b>'.$event->sender->name.'</b>';

    }

    

    public function getUpperName($event)

    {

        $event->sender->name=strtoupper($event->sender->name);

    }


}

?>

And the attachment is:




        $contest=Quiz::model()->findByPk(20);

        $cxtest = new CXTest;


        $contest->attachEventHandler('onBeforeGetName', array($cxtest, 'getBoldName'));

        $contest->attachEventHandler('onBeforeGetName', array($cxtest, 'getUpperName'));


        echo $contest->getName();

This is just great;) but the question is, how we suppose to discover all of these goodies ?

8

The only reason I ask is that generally the model data shouldn’t be modified for presentation reasons. It breaks the MVC paradigm and it only takes another developer to do a $model->save() to lead to data corruption. Unless you put logic in to reverse the modifications beforeSave. For the examples you gave it adds a load of overhead to the application as well.

9

@Say_Ten - you are perfectly right about the save() method and it’s implications in my case. Though i will not call this method your point is still valid and makes sense.

Maybe handling the model contents to a component and attach events to that component instead of the model ?

then in the views use something like <?php echo Yii::app()->contest->getName(); ?> ?

Yes, it adds some overhead and complexity, but the thing is that i would really want to have this feature active.

Anyway, if you have other suggestions, i am open to ideas.

Thanks.