/**
* Disable fields depending on product type
*
* @return $this
*/
protected function _disableFields()
{
if ($this->getDisabled() || $this->_isProductComposite()) {
$this->_qty->setDisabled('disabled');
}
if (!$this->_isProductComposite() && $this->_qty->getValue() === null) {
$this->setDisabled('disabled');
}
if ($this->isLocked()) {
$this->_qty->lock();
}
return $this;
}