CBaseController

public function beginCache($id,$properties=array())
{
    $properties['id']=$id;
    $cache=$this->beginWidget('COutputCache',$properties);
    if($cache->getIsContentCached())
    {
        $this->endCache();
        return false;
    }
    else
        return true;
}

public function beginClip($id,$properties=array())
{
    $properties['id']=$id;
    $this->beginWidget('CClipWidget',$properties);
}

public function beginContent($view=null,$data=array())
{
    $this->beginWidget('CContentDecorator',array('view'=>$view, 'data'=>$data));
}

public function beginWidget($className,$properties=array())
{
    $widget=$this->createWidget($className,$properties);
    $this->_widgetStack[]=$widget;
    return $widget;
}

public function createWidget($className,$properties=array())
{
    $widget=Yii::app()->getWidgetFactory()->createWidget($this,$className,$properties);
    $widget->init();
    return $widget;
}

public function endCache()
{
    $this->endWidget('COutputCache');
}

public function endClip()
{
    $this->endWidget('CClipWidget');
}

public function endContent()
{
    $this->endWidget('CContentDecorator');
}

public function endWidget($id='')
{
    if(($widget=array_pop($this->_widgetStack))!==null)
    {
        $widget->run();
        return $widget;
    }
    else
        throw new CException(Yii::t('yii','{controller} has an extra endWidget({id}) call in its view.',
            array('{controller}'=>get_class($this),'{id}'=>$id)));
}

abstract public function getViewFile($viewName);

public function renderFile($viewFile,$data=null,$return=false)
{
    $widgetCount=count($this->_widgetStack);
    if(($renderer=Yii::app()->getViewRenderer())!==null && $renderer->fileExtension==='.'.CFileHelper::getExtension($viewFile))
        $content=$renderer->renderFile($this,$viewFile,$data,$return);
    else
        $content=$this->renderInternal($viewFile,$data,$return);
    if(count($this->_widgetStack)===$widgetCount)
        return $content;
    else
    {
        $widget=end($this->_widgetStack);
        throw new CException(Yii::t('yii','{controller} contains improperly nested widget tags in its view "{view}". A {widget} widget does not have an endWidget() call.',
            array('{controller}'=>get_class($this), '{view}'=>$viewFile, '{widget}'=>get_class($widget))));
    }
}

public function renderInternal($_viewFile_,$_data_=null,$_return_=false)
{
    // we use special variable names here to avoid conflict when extracting data
    if(is_array($_data_))
        extract($_data_,EXTR_PREFIX_SAME,'data');
    else
        $data=$_data_;
    if($_return_)
    {
        ob_start();
        ob_implicit_flush(false);
        require($_viewFile_);
        return ob_get_clean();
    }
    else
        require($_viewFile_);
}

public function widget($className,$properties=array(),$captureOutput=false)
{
    if($captureOutput)
    {
        ob_start();
        ob_implicit_flush(false);
        try
        {
            $widget=$this->createWidget($className,$properties);
            $widget->run();
        }
        catch(Exception $e)
        {
            ob_end_clean();
            throw $e;
        }
        return ob_get_clean();
    }
    else
    {
        $widget=$this->createWidget($className,$properties);
        $widget->run();
        return $widget;
    }
}