Phalcon: How to get/validate related objects before saving?

Question

I have a model Audio and a model AudioCategory.
When I save the audio object, I want to validate that there is at least 1 audiocategory attached to it.

I created a custom validator for that.
I tried using the $audio->getRelated() in the validator, but it keeps trying to fetch in the database for the info. Since the validation occurs before saving (which is great), then I receive an empty list, thus my validator always returns false.

When I print the audio object without saving, I can see my audiocategory in the field _related of the audio object (print_r($audio);):
[_related:protected] => Array
( [audiocategory] => Array
(
[0] => GRQ\Audio\AudioCategory Object ([...])
[1] => GRQ\Audio\AudioCategory Object ([...])
)
)

If I try to print $audio->audiocategory directly, I get a notice:
Access to undefined property GRQ\Audio\Audio::audiocategory
and nothing is returned.

If I call $audio->getRelated(), I get an object of type Phalcon\Mvc\Model\Resultset\Simple with an empty _result. (Which is logic, since it went and searched in the database...)

---

Therefore, my question is:
How can I get and validate the related fields before saving them?

---

Here is my (shortened) controller test:

    $audioCategory = new AudioCategory();
    $audioCategory->categoryId = 1;
    $arAudioCategory[0] = $audioCategory; 

    $audioCategory = new AudioCategory();
    $audioCategory->categoryId = 2;
    $arAudioCategory[1] = $audioCategory;

    $audio = new Audio();
    [...other fields initialization...]
    $audio->audiocategory = $arAudioCategory;
    $audio->save();

Here is the (shortened) audio model:

namespace GRQ\Audio;
use GRQ\Validator\PresenceOfRelationValidator;
class Audio extends \Phalcon\Mvc\Model {
/**
 * @Primary
 * @Identity
 * @Column(type="integer", nullable=false)
 */
public $id = 0; 
/**
 * @Column(type="integer", nullable=false)
 */
public $createdAt = 0;

[...other fields all reflecting the database...]

public function initialize() {
    $this->setSource ( "audio" );

    // table relationships
    $this->hasMany ( "id", "GRQ\Audio\AudioCategory", "audioId", array(
            'alias' => 'audiocategory'
    ) );
}

public function validation() {      
    [...other validations...]

    $this->validate ( new PresenceOfRelationValidator ( array (
            "field" => "audiocategory" 
    ) ) );

    return $this->validationHasFailed () != true;
}
}

Here is the (shortened) audio category model:

namespace GRQ\Audio;    
class AudioCategory extends \Phalcon\Mvc\Model {
/**
 * @Primary
 * @Identity
 * @Column(type="integer", nullable=false)
 */
public $id = 0; 
/**
 * @Column(type="integer", nullable=false)
 */
public $audioId = 0;    
/**
 * @Column(type="integer", nullable=false)
 */
public $categoryId = 0;

public function initialize(){
    $this->setSource("audiocategory");
    //table relationships
    $this->belongsTo("audioId", "GRQ\Audio\Audio", "id", array(
            'alias' => 'audio'
    ));
}
}

Here is my custom validator (which doesn't work and always returns false):

namespace GRQ\Validator;

use Phalcon\Mvc\Model\Validator;
use Phalcon\Mvc\Model\ValidatorInterface;

class PresenceOfRelationValidator extends Validator implements ValidatorInterface {
public function validate($model){
    $field = $this->getOption('field');
    $message = $this->getOption('message');
    if (!$message) {
        $message = 'The required relation '.$field.' was not found';
    }

    $value = $model->getRelated($field);

    if (count($value) == 0) {
        $this->appendMessage(
                $message,
                $field,
                "PresenceOfRelation"
        );
        return false;
    }
    return true;
}
}

Answer 1

So, I found a way of achieving this. Not sure it is the best way, but it works:
Since the values are protected, I had to expose them from my object.
So I created a Base Model from which to extend myself:

Base Model:

namespace GRQ;
class BaseModel extends \Phalcon\Mvc\Model {

/**
 * This function should be used to get the data in the _related field directly.
 * It is very useful if you need to validate the presence of a relation BEFORE saving in the database.
 * To initialize the field with the database content, use $this->getRelated().
 */
public function getInternalRelated(){
    return $this->_related;
}   
}

Then I changed my audio class to extend from my base model:

Audio Model (simplified):

namespace GRQ\Audio;

use Phalcon\Mvc\Model\Validator\Numericality;
use GRQ\Validator\MinValueValidator;
use GRQ\Validator\PresenceOfRelationValidator;

class Audio extends \GRQ\BaseModel {
/**
 * @Primary
 * @Identity
 * @Column(type="integer", nullable=false)
 */
public $id = 0;

/**
 * @Column(type="string", length=255, nullable=false)
 */
public $title = '';

public function initialize() {
    $this->setSource ( "audio" );

    // table relationships
    $this->hasMany ( "id", "GRQ\Audio\AudioCategory", "audioId", array(
            'alias' => 'audiocategory'
    ) );
}

public function validation() {              
    $this->validate ( new PresenceOfRelationValidator ( array (
            "field" => "audiocategory" 
    ) ) );

    return $this->validationHasFailed () != true;
}
}

My AudioCategory model (simplified) stayed pretty much the same:

namespace GRQ\Audio;

use Phalcon\Mvc\Model\Message;

class AudioCategory extends \GRQ\BaseModel {
/**
 * @Primary
 * @Identity
 * @Column(type="integer", nullable=false)
 */
public $id = 0;

/**
 * @Column(type="integer", nullable=false)
 */
public $audioId = 0;

/**
 * @Column(type="integer", nullable=false)
 */
public $categoryId = 0;

public function initialize()
{
    $this->setSource("audiocategory");
    //table relationships
    $this->belongsTo("audioId", "GRQ\Audio\Audio", "id", array(
            'alias' => 'audio'
    ));
}
}

And my Validator now uses the method getInternalRelated to validate:

namespace GRQ\Validator;

use Phalcon\Mvc\Model\Validator;
use Phalcon\Mvc\Model\ValidatorInterface;

class PresenceOfRelationValidator extends Validator implements ValidatorInterface {
public function validate($model){
    $field = $this->getOption('field');
    $message = $this->getOption('message');
    if (!$message) {
        $message = 'The required relation '.$field.' was not found';
    }

    $value = $model->getInternalRelated();

    if (count($value[$field]) == 0) {
        $this->appendMessage(
                $message,
                $field,
                "PresenceOfRelation"
        );
        return false;
    }
    return true;
}
}