public function put(IECartPosition $position, $quantity = 1)
{
$key = $position->getId();
if ($this->itemAt($key) instanceof IECartPosition) {
$position = $this->itemAt($key);
$oldQuantity = $position->getQuantity();
$quantity += $oldQuantity;
}
$this->update($position, $quantity);
$this->eventManager->fire(CartEvents::CART_ADD_ITEM, new CartEvent(Yii::app()->getUser(), $this));
}