class CustomerRankExtension extends AbstractTypeExtension
{

    /**
     * @var CustomerRankRepository
     */
    private $customerRankRepository;


    /**
     * CustomerRankController constructor.
     * @param CustomerRankRepository $customerRankRepository
     */
    public function __construct(CustomerRankRepository $customerRankRepository)
    {
        $this->customerRankRepository = $customerRankRepository;
    }

    public function buildForm(FormBuilderInterface $builder, array $options)
    {

        $CustomerRanks = $this->customerRankRepository->getList();
        $choices = [];
        foreach($CustomerRanks as $CustomerRank){
            $choices[$CustomerRank->getId()] = $CustomerRank->getName();
        }

        $builder
        ->add(
            'CustomerRank',
            ChoiceType::class,
            [
                'label' => trans('customerrank.common.rank'),
                'required' => false,
                'mapped' => true,
                'placeholder' => "ご希望のコースを選択してください",
                'choices' => array_flip($choices),
            ]
        );
    }

    /**
     * {@inheritdoc}
     */
    public function getExtendedType()
    {
        return EntryType::class;
    }

}

Expected argument of type "Plugin\CustomerRank\Entity\CustomerRank or null", "integer" given

public function setCustomerRank(\Plugin\CustomerRank\Entity\CustomerRank $customerRank = null)
    {
        $this->CustomerRank = $customerRank;

        return $this;
    }

    public function getCustomerRank()
    {
        return $this->CustomerRank;
    }

public function setCustomerRank($customerRank)
        {
            $this->CustomerRank = $customerRank;

            return $this;
        }


        public function getCustomerRank()
        {
            return $this->CustomerRank;
        }

Expected value of type "Plugin\CustomerRank\Entity\CustomerRank" for association field "Eccube\Entity\Customer#$CustomerRank", got "integer" instead.

$this->entityManager->flush();