Yii Active Record instance with "ifModified then ..." logic and dependencies clearing

ModActiveRecord.php

<?php

/**
 * Class ModActiveRecord is the base class for classes representing relational data.
 * It provides methods to check if attributes were modified
 * 
 * @author pavel.volyntsev@gmail.com
 * @link http://copi.st/JtvJ
 * @link http://www.yiiframework.com/extension/mod-active-record/
 * 
 * @usage see sample_01_clear_relations.php and sample_02_beforeSave_ifModified.php
 */
class ModActiveRecord extends CActiveRecord
{
	protected $_modified = array();

	/**
	 * Sets the named attribute value.
	 * Also mark this attribute as modified
	 * @see CActiveRecord::setAttribute
	 */
	public function setAttribute($name,$value)
	{
		$oldValue = $this->getAttribute($name);
		if ($retValue = parent::setAttribute($name,$value))
		{
			if (!isset($this->_modified[$name]))
				$this->_modified[$name] = array('new' => $value, 'old' => $oldValue);
			else
				$this->_modified[$name]['new'] = $value;

			if ($this->_modified[$name]['new'] == $this->_modified[$name]['old'])
				unset($this->_modified[$name]);

			// clear relations that are depends on modified attribute
			/** @var \CActiveRelation $relation */
			foreach($this->getMetaData()->relations as $relationName => $relation)
				if ($name == $relation->foreignKey)
					unset($this->$relationName);
		}
		return $retValue;
	}

	/**
	 * Returns true if attribute $name was modified. If $name not set, returns true if any attribute were modified
	 */
	public function getIsModified($name = null)
	{
		if (is_null($name))
			return !empty($this->_modified);
		else
			return isset($this->_modified[$name]);
	}

	/**
	 * Resets modified marks of attribute named $name or all attributes
	 */
	public function resetModified($name = null)
	{
		if (is_null($name))
			$this->_modified = array();
		else
			unset($this->_modified[$name]);
	}

	/**
	 * Returns pair of original and modified values for attribute named $name or list of pairs for all modified attributes
	 *
	 * @return array
	 */
	public function getModified($name = null)
	{
		if (is_null($name))
			return $this->_modified;
		elseif (isset($this->_modified[$name]))
			return $this->_modified[$name];
		else
			return false;
	}

	/**
	 * Saves the current record. After that reset modified marks
	 *
	 * @see CActiveRecord::save
	 */
	public function save($runValidation=true, $attributes=null)
	{
		if ($retVal = parent::save($runValidation, $attributes))
		{
			$this->resetModified();
		}
		return $retVal;
	}
}

sample.sql

DROP TABLE IF EXISTS `book`;
DROP TABLE IF EXISTS `author`;


CREATE TABLE `author` (
  `author_id` INT(11) AUTO_INCREMENT,
  `name` VARCHAR(255) NOT NULL,
  PRIMARY KEY (`author_id`)
) ENGINE=InnoDB AUTO_INCREMENT=1 DEFAULT CHARSET=utf8;

CREATE TABLE `book` (
  `book_id` INT(11) AUTO_INCREMENT,
  `author_id` INT(11) NOT NULL,
  `title` VARCHAR(255) NOT NULL,
  PRIMARY KEY (`book_id`),
  CONSTRAINT `fk_book_author` FOREIGN KEY (`author_id`) REFERENCES `author` (`author_id`) ON DELETE CASCADE
) ENGINE=InnoDB AUTO_INCREMENT=1 DEFAULT CHARSET=utf8;

INSERT INTO `author` (`author_id`, `name`)
  VALUES
    (1,'Jack London'),
    (2,'Herman Melville'),
    (3,'Jane Austen'),
    (4,'Jonathan Swift'),
    (5,'Mark Twain');

INSERT INTO `book` (`book_id`, `author_id`, `title`)
  VALUES
  (1,1,'White Fang'),
  (2,2,'Moby-Dick, or The Whale'),
  (3,3,'Pride and Prejudice'),
  (4,4,'Gulliver\'s Travels'),
  (5,5,'The Adventures Of Huckleberry Finn');
  
  
-- mysql> SELECT b.book_id, b.title, b.author_id, a.name FROM book b JOIN author a ON a.author_id = b.author_id;
-- +---------+------------------------------------+-----------+-----------------+
-- | book_id | title                              | author_id | name            |
-- +---------+------------------------------------+-----------+-----------------+
-- |       1 | White Fang                         |         1 | Jack London     |
-- |       2 | Moby-Dick, or The Whale            |         2 | Herman Melville |
-- |       3 | Pride and Prejudice                |         3 | Jane Austen     |
-- |       4 | Gulliver's Travels                 |         4 | Jonathan Swift  |
-- |       5 | The Adventures Of Huckleberry Finn |         5 | Mark Twain      |
-- +---------+------------------------------------+-----------+-----------------+

sample_01_clear_relations.php

<?php

# In this sample two Active Record classes are used. Class Author is related with Book. 


/**
 * This is the model class for table "author".
 *
 * The followings are the available columns in table 'author':
 * @property string $author_id
 * @property string $name
 */
class Author extends CActiveRecord {

	/**
	 * @return string the associated database table name
	 */
	public function tableName()
	{
		return 'author';
	}

	/**
	 * Returns the static model of the specified AR class.
	 * @return Author the static model class
	 */
	public static function model()
	{
		return parent::model(get_called_class());
	}
}

/**
 * This is the model class for table "book".
 *
 * The followings are the available columns in table 'book':
 * @property string $book_id
 * @property string $title
 * @property string $author_id
 *
 * The followings are the available model relations:
 * @property Author $author
 */
class Book extends ModActiveRecord {

	/**
	 * @return string the associated database table name
	 */
	public function tableName()
	{
		return 'book';
	}

	/**
	 * @return array relational rules.
	 */
	public function relations()
	{
		return array(
			'author' => array(self::BELONGS_TO, 'Author', 'author_id'),
		);
	}

	/**
	 * Returns the static model of the specified AR class.
	 * @return Book the static model class
	 */
	public static function model()
	{
		return parent::model(get_called_class());
	}
}



$book = Book::model()->findByPk(1);
echo '#', $book->book_id, '. "', $book->title, '" by #', $book->author_id, '. ', $book->author->name, "\n";

# change the author_id attribute
$book->author_id = 2;
echo '#', $book->book_id, '. "', $book->title, '" by #', $book->author_id, '. ', $book->author->name, "\n";

# wrong output if class Book extends CActiveRecord
> #1. "White Fang" by #1. Jack London
> #1. "White Fang" by #2. Jack London <-- attribute $book->author_id was changed
                                          but $book->author is associated previously initialized instance

# correct output if class Book extends ModActiveRecord
> #1. "White Fang" by #1. Jack London
> #1. "White Fang" by #2. Herman Melville <-- author_id was changed cause the reinitialize of $book->author

sample_02_beforeSave_ifModified.php

<?php

# In this sample two Active Record classes are used. Class Book has beforeSave logic if author_id attribute is modified 

/**
 * This is the model class for table "author".
 *
 * The followings are the available columns in table 'author':
 * @property string $author_id
 * @property string $name
 */
class Author extends CActiveRecord {

	/**
	 * @return string the associated database table name
	 */
	public function tableName()
	{
		return 'author';
	}

	/**
	 * Returns the static model of the specified AR class.
	 * @return Author the static model class
	 */
	public static function model()
	{
		return parent::model(get_called_class());
	}
}

/**
 * This is the model class for table "book".
 *
 * The followings are the available columns in table 'book':
 * @property string $book_id
 * @property string $title
 * @property string $author_id
 *
 * The followings are the available model relations:
 * @property Author $author
 */
class Book extends ModActiveRecord {

	/**
	 * @return string the associated database table name
	 */
	public function tableName()
	{
		return 'book';
	}

	/**
	 * @return array relational rules.
	 */
	public function relations()
	{
		return array(
			'author' => array(self::BELONGS_TO, 'Author', 'author_id'),
		);
	}

	/**
	 * Do something before save() when author_id attribute is modified
	 */
	public function beforeSave()
	{
		$authorModified = $this->getModified('author_id');
		if ($authorModified)
		{
			$booksCollection = new BooksCollectionCache;
			if ($authorModified['old'])
				echo "Say 'Goodbye!' to author #", $authorModified['old'], "\n";
			if ($authorModified['new'])
				echo "Say 'Hello!' to author #", $authorModified['new'], "\n";
		}
		return true;
	}


	/**
	 * Returns the static model of the specified AR class.
	 * @return Book the static model class
	 */
	public static function model()
	{
		return parent::model(get_called_class());
	}
}


$book = Book::model()->findByPk(1);
echo '#', $book->book_id, '. "', $book->title, '" by author #', $book->author_id, "\n";

$book->author_id = 2; // change author and save
$book->save();

# wrong output if class Book extends CActiveRecord
> #1. "White Fang" by author #1
> Save... <-- attribute $book->author_id was changed but beforeSave() don't know about it
> ... saved

# correct output if class Book extends ModActiveRecord
> #1. "White Fang" by author #1
> Save...
> Say 'Goodbye!' to author #1
> Say 'Hello!' to author #2
> ... saved