Item.php

<?php

/**
 * Item class file.
 */
class Item extends CActiveRecord
{
	...
	/**
	 * @see CModel::rules()
	 */
	public function rules()
	{
		return array(
			array('title', 'length', 'max'=>50),
			array(
				'image',
				'file',
				'safe' => true,
				//'allowEmpty' => true,
				'types' => 'jpg,png,gif',
				'maxSize' => 1024*1024*1,
				'message' => '{attribute}が未選択です',
				'on' => 'insert,change',
			),
		);
	}

	/**
	 * @see CModel::behaviors()
	 */
	public function behaviors()
	{
		return array(
			'ImageUploadBehavior' => array(
				'class' => 'application.components.ImageUploadBehavior',
				'createThumb' => true,
			),
		);
	}
}