<?php

class FilePage extends Page {

static $has_one = array(
'MyFile' => 'File'
);

function getCMSFields(){
$fields = parent::getCMSFields();

$fields->addFieldsToTab('Root.Content', array(
new FileIFrameField('MyFile', 'My File')
));

return $fields;
}
}

class FilePage_Controller extends Page_Controller {
public function download(){

$assetID = $this->request->param('ID');

$do = DataObject::get_by_id('File', $assetID);

if($do && file_exists($do->URL)){
return SS_HTTPRequest::send_file(file_get_contents($do->URL), $do->Name);
}else{
echo 'error with ' . $do->URL . ' (' . file_exists($do->URL) . ')';
return false;
}

}
}

ERROR [User Error]: Uncaught Exception: Object->__call(): the method 'settabset' does not exist on 'FileIFrameField'
IN POST /newsite/admin/getitem?ID=60&ajax=1
Line 724 in /var/www/vhosts/kjebb2.com/httpdocs/newsite/sapphire/core/Object.php

Source
======
715:             
716:             default :
717:                throw new Exception (
718:                   "Object->__call(): extra method $method is invalid on $this->class:" . var_export($config,
true)
719:                );
720:          }
721:       } else {
722:          // Please do not change the exception code number below.
723:          
* 724:          throw new Exception("Object->__call(): the method '$method' does not exist on '$this->class'",
2175);
725:       }
726:    }
727:    
728:    //
-----------------------------------------------------------------------------------------------------------------
729:    
730:    /**

Trace
=====
<ul>Object->__call(setTabSet,Array)

FileIFrameField->setTabSet(TabSet)
line 128 of TabSet.php

TabSet->push(FileIFrameField)
line 128 of FieldSet.php

FieldSet->addFieldsToTab(Root.Content,Array)
line 14 of FilePage.php

FilePage->getCMSFields(CMSMain)
line 441 of CMSMain.php

CMSMain->getEditForm(60)
line 1039 of LeftAndMain.php

LeftAndMain->EditForm()
line 389 of LeftAndMain.php

LeftAndMain->getitem(SS_HTTPRequest)
line 193 of Controller.php

Controller->handleAction(SS_HTTPRequest)
line 143 of RequestHandler.php

RequestHandler->handleRequest(SS_HTTPRequest)
line 147 of Controller.php

Controller->handleRequest(SS_HTTPRequest)
line 282 of Director.php

Director::handleRequest(SS_HTTPRequest,Session)
line 125 of Director.php

Director::direct(/admin/getitem)
line 127 of main.php

</ul>