Trying to add a protocol to a Class signature in swift

问题

I'm trying to create an in-app purchase in swift. In my class signature, I have the following:

class ViewController: UIViewController, UITextFieldDelegate, UIAlertViewDelegate,   
SKStoreProductViewControllerDelegate, SKPaymentTransactionObserver{

However, I get an error message: type "ViewController" does not conform to protocol: SKPaymentTransactionObserver

I've read this: https://developer.apple.com/library/prerelease/mac/documentation/Swift/Conceptual/BuildingCocoaApps/WritingSwiftClassesWithObjective-CBehavior.html and Conform to protocol in ViewController, in Swift

The SKSoreProductViewControllerDelegate works fine. What am I missing, please?

回答1:

Have you implemented the required methods in your class?

paymentQueue:updatedTransactions: and paymentQueue:updatedDownloads: are required methods and you will get a warning if they are not implemented.

回答2:

SKPaymentTransactionProtocol has these methods:

func paymentQueue(queue: SKPaymentQueue!, updatedTransactions transactions: [AnyObject]!) 
@optional func paymentQueue(queue: SKPaymentQueue!, removedTransactions transactions: [AnyObject]!)
@optional func paymentQueue(queue: SKPaymentQueue!, restoreCompletedTransactionsFailedWithError error: NSError!)
@optional func paymentQueueRestoreCompletedTransactionsFinished(queue: SKPaymentQueue!)
@optional func paymentQueue(queue: SKPaymentQueue!, updatedDownloads downloads: [AnyObject]!)

The first is a required method that your class has to implement in order to conform to the protocol. Add it to your ViewController and the error will disappear.

class ViewController: UIViewController, UITextFieldDelegate, UIAlertViewDelegate,   
SKStoreProductViewControllerDelegate, SKPaymentTransactionObserver{
    func paymentQueue(queue: SKPaymentQueue!, updatedTransactions transactions: [AnyObject]!){/*...*/}
    /*...*/
}

回答3:

For swift use this:

public func paymentQueue(queue: SKPaymentQueue, updatedTransactions transactions: [SKPaymentTransaction]) { /* */ }

Instead of this:

public func paymentQueue(queue: SKPaymentQueue!, updatedTransactions transactions: [AnyObject]!) { /* */ }

来源：https://stackoverflow.com/questions/24588531/trying-to-add-a-protocol-to-a-class-signature-in-swift