Uncaught Error: Function name must be a string magento 2

Question

Fatal error: Uncaught Error: Function name must be a string in /Applications/MAMP/htdocs/magentoshop/app/code/Magestore/couponoverride/Model/CouponManagement.php:74

Stack trace:

#0 [internal function]: Magestore\couponoverride\Model\CouponManagement->set(53694, 'special')
#1 /Applications/MAMP/htdocs/magentoshop/vendor/magento/module-webapi/Controller/Rest.php(330):
call_user_func_array(Array, Array)
#2 /Applications/MAMP/htdocs/magentoshop/vendor/magento/module-webapi/Controller/Rest.php(239):
Magento\Webapi\Controller\Rest->processApiRequest()
#3 /Applications/MAMP/htdocs/magentoshop/vendor/magento/framework/Interception/Interceptor.php(58):
Magento\Webapi\Controller\Rest->dispatch(Object(Magento\Framework\App\Request\Http))
#4 /Applications/MAMP/htdocs/magentoshop/vendor/magento/framework/Interception/Interceptor.php(138):
Magento\Webapi\Controller\Rest\Interceptor->___callParent('dispatch', Array)
#5 /Applications/MAMP/htdocs/magentoshop/vendor/magento/framework/Interception/Interceptor.php(153):
Magento\Webapi\Contro in
<b>/Applications/MAMP/htdocs/magentoshop/app/code/Magestore/couponoverride/Model/CouponManagement.php</b> on line
<b>74</b><br />
{"messages":{"error":[{"code":500,"message":"Fatal Error: 'Uncaught Error: Function name must be a string in \/Applications\/MAMP\/htdocs\/magentoshop\/app\/code\/Magestore\/couponoverride\/Model\/CouponManagement.php:74\nStack trace:\n#0 [internal function]: Magestore\\couponoverride\\Model\\CouponManagement->set(53694, 'special')\n#1 \/Applications\/MAMP\/htdocs\/magentoshop\/vendor\/magento\/module-webapi\/Controller\/Rest.php(330): call_user_func_array(Array, Array)\n#2 \/Applications\/MAMP\/htdocs\/magentoshop\/vendor\/magento\/module-webapi\/Controller\/Rest.php(239): Magento\\Webapi\\Controller\\Rest->processApiRequest()\n#3 \/Applications\/MAMP\/htdocs\/magentoshop\/vendor\/magento\/framework\/Interception\/Interceptor.php(58): Magento\\Webapi\\Controller\\Rest->dispatch(Object(Magento\\Framework\\App\\Request\\Http))\n#4 \/Applications\/MAMP\/htdocs\/magentoshop\/vendor\/magento\/framework\/Interception\/Interceptor.php(138): Magento\\Webapi\\Controller\\Rest\\Interceptor->___callParent('dispatch', Array)\n#5 \/Applications\/MAMP\/htdocs\/magentoshop\/vendor\/magento\/framework\/Interception\/Interceptor.php(153): Magento\\Webapi\\Contro' in '\/Applications\/MAMP\/htdocs\/magentoshop\/app\/code\/Magestore\/couponoverride\/Model\/CouponManagement.php' on line 74","trace":"Trace is not available."}]}}

My app/code/Magestore/couponoverride/Model/CouponManagement.php:

<?php
/**
 *
 * Copyright © Magento, Inc. All rights reserved.
 * See COPYING.txt for license details.
 */

namespace Magestore\couponoverride\Model;

use Magento\Framework\Exception\LocalizedException;
use Magestore\couponoverride\Api\CouponManagementInterface;
use Magento\Framework\Exception\CouldNotDeleteException;
use Magento\Framework\Exception\CouldNotSaveException;
use Magento\Framework\Exception\NoSuchEntityException;
use Magento\SalesRule\Model\Rule\Action\Discount\AbstractDiscount;
/**
 * Coupon management object.
 */
class CouponManagement implements CouponManagementInterface
{
    /**
     * Quote repository.
     *
     * @var \Magento\Quote\Api\CartRepositoryInterface //\Magento\SalesRule\Model\Coupon
     */
    protected $quoteRepository;
    protected $coupon;
    protected $saleRule; 

    /**
     * Constructs a coupon read service object.
     *
     * @param \Magento\Quote\Api\CartRepositoryInterface $quoteRepository Quote repository.
     */
    public function __construct(
        \Magento\Quote\Api\CartRepositoryInterface $quoteRepository,
        \Magento\SalesRule\Model\Coupon $coupon,

        \Magento\SalesRule\Model\Rule $saleRule,
        \Magento\Quote\Model\Quote\Address\Total $total
    ) {
        $this->quoteRepository = $quoteRepository;
        $this->coupon=$coupon;
        $this->saleRule = $saleRule;

      }

    // /**
    //  * @inheritDoc
    //  */
    // public function get($cartId)
    // {
    //     /** @var  \Magento\Quote\Model\Quote $quote */
    //     $quote = $this->quoteRepository->getActive($cartId);
    //    // echo "tmkoc";
    //     return $quote->getCouponCode();
    // }

   /**
     * Adds a coupon by code to a specified cart.
     *
     * @param int $cartId The cart ID.
     * @param string $couponCode The coupon code data.
     * @return bool
     * @throws \Magento\Framework\Exception\NoSuchEntityException The specified cart does not exist.
     * @throws \Magento\Framework\Exception\CouldNotSaveException The specified coupon could not be added.
     */
    public function set( $cartId, $couponCode)
    {
        /** @var  \Magento\Quote\Model\Quote $quote */
        $couponCode=trim($couponCode);
        $quote = $this->quoteRepository->getActive($cartId);

    $items = $quote()->getAllItems();

         if (!$quote->getItemsCount()) {
            throw new NoSuchEntityException(__('The "%1" Cart doesn\'t contain products.', $cartId));
        }
        if (!$quote->getStoreId()) {
            throw new NoSuchEntityException(__('Cart isn\'t assigned to correct store'));
        }
      //  $quote->getShippingAddress()->setCollectShippingRates(true);

        $subtotalInclTax = 0;

        try {

              foreach($items as $item) {

                    $subtotalInclTax += $item->getRowTotalInclTax();

                      $qty=$item->getQty();
                       $price=$item->getPrice();
                          $total+=$price*$qty;
                $item->getShippingAddress()->setCollectShippingRates(true);
                      if($item->getPrice()==$item->getFinalPrice())
                      {
                        //$item->setcouponamount($couponCode);


                        $discount+=setcouponamount($couponCode,$item,$qty);
                        if($discount== -1)
                        {
                           $quote->setCouponCode($couponCode);
                           $this->quoteRepository->save($quote->collectTotals());
                          break;
                        }
                      }  

            }
            if($amount!=-1)
            {
              $total2=$total-$discount;
              $quote->setSubtotal($total);
              $quote->setBaseSubtotal($total);
              $quote->setDiscountAmount($discount);
              $quote->setBaseDiscountAmount($discount);
              $quote->setSubtotalWithDiscount($total2);
              $quote->setBaseSubtotalWithDiscount($total2);
              $quote->setSubtotalInclTax($subtotalInclTax);
              $quote->setGrandTotal($subtotalInclTax-$discount);
              $quote->setBaseGrandTotal($subtotalInclTax-$discount);
            //  $quote->setcoupon
              $quote->save();



          }
          echo $total;
          echo $amount;
          echo $total2;

         //   $quote->setCouponCode($couponCode);
           // $this->quoteRepository->save($quote->collectTotals());
        } catch (LocalizedException $e) {
            throw new CouldNotSaveException(__('The coupon code couldn\'t be applied: ' .$e->getMessage()), $e);
        } catch (\Exception $e) {
            throw new CouldNotSaveException(
                __("The coupon code couldn't be applied. Verify the coupon code and try again."),
                $e
            );
        }
        //if ($quote->getCouponCode() != $couponCode) {
          //  throw new NoSuchEntityException(__("The coupon code isn't valid. Verify the code and try again."));
        //}
        exit(0);
        return true;
    }
    // *
    // *inhertdoc
    // *
     public function setcouponamount($couponCode,$item,$qty)
     {
        $ruleId =   $this->coupon->loadByCode($couponCode)->getRuleId();
        $rule = $this->saleRule->load($ruleId);
        //return $rule->getDiscountAmount();
      //  $amount=$rule->(int)getDiscountAmount();
       // return $amount;
        if($rule->getSimpleAction()=="by_percent")
        {
          //$amount=$rule->getDiscountAmount();
            $rulePercent = min(100, $rule->getDiscountAmount());
               $discountData = $this->discountFactory->create();

        $itemPrice = $this->validator->getItemPrice($item);
        $baseItemPrice = $this->validator->getItemBasePrice($item);
        $itemOriginalPrice = $this->validator->getItemOriginalPrice($item);
        $baseItemOriginalPrice = $this->validator->getItemBaseOriginalPrice($item);

        $_rulePct = $rulePercent / 100;

        $taxAmount = $itemPrice - ($itemPrice / ((100 + $item->getTaxPercent())/100));
        $perItemTaxAmount = $taxAmount;
        $itemPriceBeforeTax = $itemPrice - $perItemTaxAmount;
        $discountData->setAmount(($qty * $itemPriceBeforeTax - $item->getDiscountAmount()) * $_rulePct);
        $discountData->setBaseAmount(($qty * ($baseItemPrice - $perItemTaxAmount) - $item->getBaseDiscountAmount()) * $_rulePct);
        $discountData->setOriginalAmount(($qty * ($itemOriginalPrice - $perItemTaxAmount) - $item->getDiscountAmount()) * $_rulePct);
        $discountData->setBaseOriginalAmount(
            ($qty * $baseItemOriginalPrice - $item->getBaseDiscountAmount()) * $_rulePct
        );

        if (!$rule->getDiscountQty() || $rule->getDiscountQty() > $qty) {
            $discountPercent = min(100, $item->getDiscountPercent() + $rulePercent);
            $item->setDiscountPercent($discountPercent);
        }

        return $discountData;

        }
        elseif($rule->getSimpleAction()=="by_fixed")
        {
             $discountData = $this->discountFactory->create();

        $quoteAmount = $this->priceCurrency->convert($rule->getDiscountAmount(), $item->getQuote()->getStore());
        $discountData->setAmount($qty * $quoteAmount);
        $discountData->setBaseAmount($qty * $rule->getDiscountAmount());

        return $discountData;
        }
        elseif($rule->getSimpleAction()=="cart_fixed")
        {
          return -1;
        }
     }


    /**
     * @inheritDoc
     */
    // public function remove($cartId)
    // {
    //     /** @var  \Magento\Quote\Model\Quote $quote */
    //     $quote = $this->quoteRepository->getActive($cartId);
    //     if (!$quote->getItemsCount()) {
    //         throw new NoSuchEntityException(__('The "%1" Cart doesn\'t contain products.', $cartId));
    //     }
    //     $quote->getShippingAddress()->setCollectShippingRates(true);
    //     try {
    //         $quote->setCouponCode('');
    //         $this->quoteRepository->save($quote->collectTotals());
    //     } catch (\Exception $e) {
    //         throw new CouldNotDeleteException(
    //             __("The coupon code couldn't be deleted. Verify the coupon code and try again.")
    //         );
    //     }
    //     if ($quote->getCouponCode() != '') {
    //         throw new CouldNotDeleteException(
    //             __("The coupon code couldn't be deleted. Verify the coupon code and try again.")
    //         );
    //     }
    //     return true;
    // }
}


***My interface is:***
<?php
/**
 *
 * Copyright © Magento, Inc. All rights reserved.
 * See COPYING.txt for license details.
 */

namespace Magestore\couponoverride\Api;

/**
 * Coupon Management service interface.
 * @api
 * @since 100.0.2
 */
interface CouponManagementInterface
{
   /**
     * Adds a coupon by code to a specified cart.
     *
     * @param int $cartId The cart ID.
     * @param string $couponCode The coupon code data.
     * @return bool
     * @throws \Magento\Framework\Exception\NoSuchEntityException The specified cart does not exist.
     * @throws \Magento\Framework\Exception\CouldNotSaveException The specified coupon could not be added.
     */
    public function set($cartId, $couponCode);
}

Answer 1

Check this code in line 74:

$items = $quote()->getAllItems();

Change it to

$items = $quote->getAllItems();

Basically if you write $quote() it means you call a method, where the method name is saved in $quote variable. Because the $quote variable store an object, not a string, then the error comes.