Swift 3 code rewritten from Objective-C doesn't work

Question

So I have this code in Objective-C which I need to rewrite to Swift3.

However it doesn't seem to work. Underneath is the Objective-C and under that my rewrite of it to Swift3:

Objective-C

- (void)handleMobilePayPaymentWithUrl:(NSURL *)url
{
    [[MobilePayManager sharedInstance]handleMobilePayPaymentWithUrl:url success:^(MobilePaySuccessfulPayment * _Nullable mobilePaySuccessfulPayment) {
        NSString *orderId = mobilePaySuccessfulPayment.orderId;
        NSString *transactionId = mobilePaySuccessfulPayment.transactionId;
        NSString *amountWithdrawnFromCard = [NSString stringWithFormat:@"%f",mobilePaySuccessfulPayment.amountWithdrawnFromCard];
        NSLog(@"MobilePay purchase succeeded: Your have now paid for order with id '%@' and MobilePay transaction id '%@' and the amount withdrawn from the card is: '%@'", orderId, transactionId,amountWithdrawnFromCard);
        [ViewHelper showAlertWithTitle:@"MobilePay Succeeded" message:[NSString stringWithFormat:@"You have now paid with MobilePay. Your MobilePay transactionId is '%@'", transactionId]];

    } error:^(NSError * _Nonnull error) {
        NSDictionary *dict = error.userInfo;
        NSString *errorMessage = [dict valueForKey:NSLocalizedFailureReasonErrorKey];
        NSLog(@"MobilePay purchase failed:  Error code '%li' and message '%@'",(long)error.code,errorMessage);
        [ViewHelper showAlertWithTitle:[NSString stringWithFormat:@"MobilePay Error %li",(long)error.code] message:errorMessage];

        //TODO: show an appropriate error message to the user. Check MobilePayManager.h for a complete description of the error codes

        //An example of using the MobilePayErrorCode enum
        //if (error.code == MobilePayErrorCodeUpdateApp) {
        //    NSLog(@"You must update your MobilePay app");
        //}
    } cancel:^(MobilePayCancelledPayment * _Nullable mobilePayCancelledPayment) {
        NSLog(@"MobilePay purchase with order id '%@' cancelled by user", mobilePayCancelledPayment.orderId);
        [ViewHelper showAlertWithTitle:@"MobilePay Canceled" message:@"You cancelled the payment flow from MobilePay, please pick a fruit and try again"];

    }];
}

And my Swift3 rewrite:

func handleMobilePayPayment(with url: URL) {
        MobilePayManager.sharedInstance().handleMobilePayPayment(with: url, success: {( mobilePaySuccessfulPayment: MobilePaySuccessfulPayment?) -> Void in
            let orderId: String = mobilePaySuccessfulPayment!.orderId
            let transactionId: String = mobilePaySuccessfulPayment!.transactionId
            let amountWithdrawnFromCard: String = "\(mobilePaySuccessfulPayment!.amountWithdrawnFromCard)"
            print("MobilePay purchase succeeded: Your have now paid for order with id \(orderId) and MobilePay transaction id \(transactionId) and the amount withdrawn from the card is: \(amountWithdrawnFromCard)")
                self.alert(message: "You have now paid with MobilePay. Your MobilePay transactionId is \(transactionId)", title: "MobilePay Succeeded")

        }, error: {( error: Error?) -> Void in
            let dict: [AnyHashable: Any]? = error?.userInfo
            let errorMessage: String? = (dict?.value(forKey: NSLocalizedFailureReasonErrorKey) as? String)
            print("MobilePay purchase failed:  Error code '(Int(error?.code))' and message '(errorMessage)'")
            self.alert(message: errorMessage!, title: "MobilePay Error \(error?.code as! Int)")
            self.alert(message: error as! String)
            //TODO: show an appropriate error message to the user. Check MobilePayManager.h for a complete description of the error codes
            //An example of using the MobilePayErrorCode enum
            //if (error.code == MobilePayErrorCodeUpdateApp) {
            //    NSLog(@"You must update your MobilePay app");
            //}
        }, cancel: {(_ mobilePayCancelledPayment: MobilePayCancelledPayment?) -> Void in
            print("MobilePay purchase with order id \(mobilePayCancelledPayment?.orderId!) cancelled by user")
            self.alert(message: "You cancelled the payment flow from MobilePay, please pick a fruit and try again", title: "MobilePay Canceled")
        })
    }

The problem's I am getting is with the error in the middle , as shown in the picture below.

I am unsure of what I am doing wrong and how to get the userInfo and the error info "out" of error.

Thanks in advance!

Answer 1

You have to bridge cast error to NSError

...
}, error: { error in   // according to the ObjC code error is non-optional 
    let nsError =  error as NSError   
    let userInfo = nsError.userInfo as! [String:Any]
    let errorMessage = userInfo[NSLocalizedFailureReasonErrorKey] as! String
    ...
    self.alert(message: errorMessage, title: "MobilePay Error \(nsError.code)")

---

Basically do not annotate types the compiler can infer and never use valueForKey to get a value from a user info dictionary.