SWIFT_CLASS("_TtC12palaceCookie18OrangeExchangeUtil")@interface OrangeExchangeUtil : NSObject <SKPaymentTransactionObserver, SKProductsRequestDelegate>- (nonnull instancetype)init OBJC_DESIGNATED_INITIALIZER;- (void)productsRequest:(SKProductsRequest * _Nonnull)request didReceiveResponse:(SKProductsResponse * _Nonnull)response;- (void)paymentQueue:(SKPaymentQueue * _Nonnull)queue updatedTransactions:(NSArray<SKPaymentTransaction *> * _Nonnull)transactions;@end}palaceCookie-Swift.h:353:43: Unknown class name 'SKPaymentTransactionObserver'; did you mean 'SKPaymentTransaction'?palaceCookie-Swift.h:353:73: Unknown class name 'SKProductsRequestDelegate'; did you mean 'SKProductsRequest'?palaceCookie-Swift.h:353:43: Type argument 'SKPaymentTransaction' must be a pointer (requires a '*')palaceCookie-Swift.h:353:73: Type argument 'SKProductsRequest' must be a pointer (requires a '*')palaceCookie-Swift.h:353:33: Type arguments cannot be applied to non-parameterized class 'NSObject'code:import Foundationimport StoreKitclass OrangeExchangeUtil: NSObject, SKProductsRequestDelegate, SKPaymentTransactionObserver {XCode 11.2 Swift 4.2How to solve this error? thankyou!