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();
}