public function setInvoice($iInvoiceId)
    {
        //  Validate
        $oModel   = $this->oInvoiceModel;
        $oInvoice = $oModel->getById(
            $iInvoiceId,
            ['expand' => $oModel::EXPAND_ALL]
        );

        if (empty($oInvoice)) {
            throw new RequestException('Invalid invoice ID.');
        }

        $this->oInvoice = $oInvoice;
        return $this;
    }