Does not conform to protocol SKPaymentTransactionObserver - swift

Question

I am trying to implement in app purchases in a Swift app, of a consumable in-app purchase, with product ID productID
Research
Using this answer, I learned about the basic pattern for in app purchases, and tried to adapt it, like so. I do not need to use the NSUserDefaults method of having the app remember if a purchase is made, as I am handling that with a different solution.
Code
class ViewController: UICollectionViewController, SKProductsRequestDelegate, SKPaymentTransactionObserver {
viewDidLoad() {
//Unimportant stuff left out
product_id = "productID"
SKPaymentQueue.defaultQueue().addTransactionObserver(self)
}
#IBAction func thisISTheButtonToTriggerTheInAppPurchases(sender: AnyObject) {
if (SKPaymentQueue.canMakePayments()) {
var productID:NSSet = NSSet(object: self.product_id!);
var productsRequest:SKProductsRequest = SKProductsRequest(productIdentifiers: productID as! Set<String>);
productsRequest.delegate = self;
productsRequest.start();
print("Fetching Products");
}else{
print("can't make purchases");
}
}
func buyProduct(product: SKProduct){
print("Sending the Payment Request to Apple");
var payment = SKPayment(product: product)
SKPaymentQueue.defaultQueue().addPayment(payment);
}
func productsRequest (request: SKProductsRequest, didReceiveResponse response: SKProductsResponse) {
var count : Int = response.products.count
if (count>0) {
var validProducts = response.products
var validProduct: SKProduct = response.products[0] as SKProduct
if (validProduct.productIdentifier == self.product_id) {
print(validProduct.localizedTitle)
print(validProduct.localizedDescription)
print(validProduct.price)
buyProduct(validProduct);
} else {
print(validProduct.productIdentifier)
}
} else {
print("nothing")
}
}
func request(request: SKRequest!, didFailWithError error: NSError!) {
print("Error Fetching product information");
}
func paymentQueue(queue: SKPaymentQueue!, updatedTransactions transactions: [AnyObject]!) {
print("Received Payment Transaction Response from Apple");
for transaction:AnyObject in transactions {
if let trans:SKPaymentTransaction = transaction as? SKPaymentTransaction{
switch trans.transactionState {
case .Purchased:
print("Product Purchased");
SKPaymentQueue.defaultQueue().finishTransaction(transaction as! SKPaymentTransaction)
break;
case .Failed:
print("Purchased Failed");
SKPaymentQueue.defaultQueue().finishTransaction(transaction as! SKPaymentTransaction)
break;
case .Restored:
print("Already Purchased");
SKPaymentQueue.defaultQueue().restoreCompletedTransactions()
default:
break;
}
}
}
}
}
Error
Type 'ViewController' does not conform to protocol 'SKPaymentTransactionObserver'
I researched this error a bit, and sources like this suggest that such an error is due to not having required functions.
According to Apple, paymentQueue:updatedTransactions: is the only one required, but I seem to be implementing that. A possible theory of mine is that I am not implementing it correctly - if true, how do I fix that?
Expected Behavior
The app presents, and if given favorable user input, performs the IAP with the ID productID.
Thanks for helping, and let me know if you need any more information!

Answer 1

It's very simple. The error is about SKPaymentTransactionObserver. Its only required method is:
func paymentQueue(queue: SKPaymentQueue,
updatedTransactions transactions: [SKPaymentTransaction])
The signature for your method doesn't match that:
func paymentQueue(queue: SKPaymentQueue!,
updatedTransactions transactions: [AnyObject]!)
...so it isn't the same method, so you don't conform.