YII框架分析笔记8：CDataProvider

CDataProvider，顾名思义，数据提供者，它提供了三个抽象方法(fetchData,、fetchKeys 和 calculateTotalItemCount)，分别为调用不同数据结构的数据提供了获取数据、获取键值、获取数量的，接口，在YII框架中，CActiveDataProvider、CArrayDataProvider、CSqlDataProvider是它的子类，除了提供数据之外，他还提供分页和排序功能。下面以获取数据fetchData()为例

CActiveDataProvider通过CActiveRecord的子类和CDbCriteria对象

/**    * Fetches the data from the persistent data storage.    * @return array list of data items    */protected function fetchData(){    $criteria=clone $this->getCriteria();    if(($pagination=$this->getPagination())!==false)    {        $pagination->setItemCount($this->getTotalItemCount());        $pagination->applyLimit($criteria);    }    $baseCriteria=$this->model->getDbCriteria(false);    if(($sort=$this->getSort())!==false)    {        // set model criteria so that CSort can use its table alias setting        if($baseCriteria!==null)        {            $c=clone $baseCriteria;            $c->mergeWith($criteria);            $this->model->setDbCriteria($c);        }        else            $this->model->setDbCriteria($criteria);        $sort->applyOrder($criteria);    }    $this->model->setDbCriteria($baseCriteria!==null ? clone $baseCriteria : null);    $data=$this->model->findAll($criteria);    $this->model->setDbCriteria($baseCriteria);  // restore original criteria    return $data;}

CArrayDataProvider通过传人的原生数据来获取数据

/**    * Fetches the data from the persistent data storage.    * @return array list of data items    */protected function fetchData(){    if(($sort=$this->getSort())!==false && ($order=$sort->getOrderBy())!='')        $this->sortData($this->getSortDirections($order));    if(($pagination=$this->getPagination())!==false)    {        $pagination->setItemCount($this->getTotalItemCount());        return array_slice($this->rawData, $pagination->getOffset(), $pagination->getLimit());    }    else        return $this->rawData;}

CSqlDataProvider通过传人的sql，经过db执行获取数据

/**    * Fetches the data from the persistent data storage.    * @return array list of data items    */protected function fetchData(){    $sql=$this->sql;    $db=$this->db===null ? Yii::app()->db : $this->db;    $db->active=true;    if(($sort=$this->getSort())!==false)    {        $order=$sort->getOrderBy();        if(!empty($order))        {            if(preg_match('/\s+order\s+by\s+[\w\s,]+$/i',$sql))                $sql.=', '.$order;            else                $sql.=' ORDER BY '.$order;        }    }    if(($pagination=$this->getPagination())!==false)    {        $pagination->setItemCount($this->getTotalItemCount());        $limit=$pagination->getLimit();        $offset=$pagination->getOffset();        $sql=$db->getCommandBuilder()->applyLimit($sql,$limit,$offset);    }    $command=$db->createCommand($sql);    foreach($this->params as $name=>$value)        $command->bindValue($name,$value);    return $command->queryAll();}