Default Model Instance on Empty Relation

[pavel-voronin]

I want to set new param (e.g. 'default', 'defaultCriteria', etc.) to CActiveRecord.relations() array, which say to CActiveFinder (or CActiveRecord?) to load default model instance (or set of instances in some relation types) in case when nothing is found in CActiveRecord.getRelated().

Use case:

// old
if ( $company->initiator ) // this block can appear multiple times in multiple variations per view
    echo $company->initiator->name;

// new
echo $company->initiator->name; // initiator populated with Default User Model if no one found

[samdark]

I don't think it will fit framework well. You can always use a method like $company->getInitiatorName().

[pavel-voronin]

No I can't if i have long relation chains like Yii::app()->user->model->favorites[0]->company->initiator->name and something happens (e.g. company status was set to 'delete' and company.defaultScope() deny this company to be fetched). Now I must check every chain element for existence.

[resurtm]

Yii::app()->user->model->favorites[0]->company->initiator->name

1. Yii::app()->user->model — i daresay you're performing SELECT * ... which is bad practice and evil. Select clause should be context-aware as much as possible.
2. $model->favorites[0] — this could be shortened to getFirstFavorite() or getFavorite().
3. $company->initiator->name — this could be shortened to getInitiatorName().

In summary:

<?php

// data definition, model
class User extends CActiveRecord
{
    public $id;
    public $first_name;

    public function relations()
    {
        return array(
            'favorites'=>array(self::HAS_MANY,'Favorite','user_id'),
            // neat way of getting single favorite related record
            'favorite'=>array(self::HAS_ONE,'Favorite','user_id'),
        );
    }
}

class Favorite extends CActiveRecord
{
    public $user_id;
    public $company_id;

    public function relations()
    {
        return array(
            'company'=>array(self::BELONGS_TO,'Company','company_id',
                'condition'=>'company.deleted=0'),
        );
    }
}

class Company extends CActiveRecord
{
    public $id;

    public function relations()
    {
        return array(
            'initiator'=>array(self::HAS_ONE,'Initiator','company_id'),
        );
    }

    public function getInitiatorName()
    {
        if($this->initiator)
        {
            return $this->initiator->name;
        }
    }
}

class Initiator extends CActiveRecord
{
    public $id;
    public $company_id;
    public $name;
}

// querying, controller
$criteria=new CDbCriteria();
$criteria->with=array(
    'favorite'=>array('select'=>false),
    'favorite.company'=>array('select'=>false),
    'favorite.company.initiator'=>array('select'=>'name'),
);
$criteria->select=array('t.id','t.first_name');
$criteria->addColumnCondition(array('t.id'=>Yii::app()->user->id));

$user=User::model()->find($criteria); // passed to the view
$favorite=$user->favorite; // passed to the view

// displaying, view
echo $user->first_name;
if($favorite!==null && $favorite->company!==null):
    echo $favorite->company->initiatorName;
endif;

Any situation could be simplified as i described above.

[pavel-voronin]

You didn't understand me, sorry.

[resurtm]

I did. You're using relations improperly. We can continue discussion in Skype or Jabber if you want.

[resurtm]

Yii::app()->user->model->favorites[0]->company->initiator->name

http://www.soberit.hut.fi/mmantyla/badcodesmellstaxonomy.htm

The Feature Envy smell means a case where one method is too interested in other classes, and the Inappropriate Intimacy smell means that two classes are coupled tightly to each other. Message Chains is a smell where class A needs data from class D. To access this data, class A needs to retrieve object C from object B (A and B have a direct reference). When class A gets object C it then asks C to get object D. When class A finally has a reference to class D, A asks D for the data it needs. The problem here is that A becomes unnecessarily coupled to classes B, C, and D, when it only needs some piece of data from class D. The following example illustrates the message chain smell: A.getB().getC().getD().getTheNeededData()