In App Purchase Crashes on [[SKPaymentQueue defaul

Question

My In-App-Purchases work. I present a ModalView with a "Buy" UIButton. You click the button and the In App Purchase goes through the process. You can even do it several times in a row.

The problem occurs if you open the Modal View, then close the Modal View (using a UITabBarButtonItem), then reopen the Modal View and tap the "Buy" button. The app crashes and I get an NSZombie that reads

*** -[InAppPurchaseManager respondsToSelector:]: message sent to deallocated instance 0x1c7ad0

The NSZombie points to line 160 in the .m file. I have marked it with comments.

I got the original code from this page: http://troybrant.net/blog/2010/01/in-app-purchases-a-full-walkthrough/

I have been struggling with this for many days now... any help would be awesome.

Here is the .h

//
//  InAppPurchaseManager.h
//  Copyright 2010 __MyCompanyName__. All rights reserved.


#import <UIKit/UIKit.h>
#import <StoreKit/StoreKit.h>

#define kInAppPurchaseManagerProductsFetchedNotification @"kInAppPurchaseManagerProductsFetchedNotification"
#define kInAppPurchaseManagerTransactionFailedNotification @"kInAppPurchaseManagerTransactionFailedNotification"
#define kInAppPurchaseManagerTransactionSucceededNotification @"kInAppPurchaseManagerTransactionSucceededNotification"

#define kInAppPurchaseCreditProductId @"com.myname.app.iap"

@interface InAppPurchaseManager : UIViewController <SKProductsRequestDelegate, SKPaymentTransactionObserver>
{
    SKProduct *productID;
    SKProductsRequest *productsRequest;

 IBOutlet UIBarButtonItem *closeButton;
 IBOutlet UIButton *buyButton;
 IBOutlet UILabel *testLabel;

}

@property (retain, nonatomic) SKProduct *productID;
@property (retain, nonatomic) SKProductsRequest *productsRequest;

@property (retain, nonatomic) IBOutlet UIBarButtonItem *closeButton;
@property (retain, nonatomic) IBOutlet UIButton *buyButton;
@property (retain, nonatomic) IBOutlet UILabel *testLabel;


// public methods
-(void)loadStore;
-(BOOL)canMakePurchases;
-(void)purchaseCredit;

-(void)requestInAppPurchaseData;
-(void)buyButtonAction:(id)sender;
-(void)closeButtonAction:(id)sender;
-(void)updateButtonStatus:(NSString *)status;

@end

Here is the .m

// InAppPurchaseManager.m

#import "InAppPurchaseManager.h"

@implementation InAppPurchaseManager

@synthesize productID;
@synthesize productsRequest;

@synthesize closeButton;
@synthesize buyButton;
@synthesize testLabel;


- (void)dealloc {

 [productID release];
 //[productsRequest release];

 [closeButton release];
 [buyButton release];
 [testLabel release];

    [super dealloc];
}


- (void)viewDidLoad {
    [super viewDidLoad];

 [closeButton release];
 closeButton = [[UIBarButtonItem alloc] initWithTitle:@"Close" style:UIBarButtonItemStyleBordered target:self action:@selector(closeButtonAction:)];
 self.navigationItem.leftBarButtonItem = closeButton;

 [self loadStore];

 self.navigationItem.title = @"Credits";


}

-(void)closeButtonAction:(id)sender { 
 [self dismissModalViewControllerAnimated:YES];
}


-(void)buyButtonAction:(id)sender {

 if([self canMakePurchases]) {
  [self updateButtonStatus:@"OFF"];

  [self performSelectorOnMainThread:@selector(requestInAppPurchaseData) withObject:nil waitUntilDone:NO];

 } else {
  UIAlertView *alertView = [[UIAlertView alloc] initWithTitle:nil message:[NSString stringWithString:@"Your account settings do not allow for In App Purchases."] delegate:self cancelButtonTitle:@"OK" otherButtonTitles:nil];
  [alertView show];
  [alertView release];  
 }

}


-(void)updateButtonStatus:(NSString *)status {

 if ([status isEqual:@"OFF"]) {
  closeButton.enabled = NO;
  buyButton.enabled = NO;
  buyButton.titleLabel.textColor = [UIColor grayColor];
 } else {
  closeButton.enabled = YES;
  buyButton.enabled = YES;
  buyButton.titleLabel.textColor = [UIColor blueColor];
 }

}

#pragma mark -
#pragma mark SKProductsRequestDelegate methods


//
// call this method once on startup
//
- (void)loadStore
{

    // restarts any purchases if they were interrupted last time the app was open
    [[SKPaymentQueue defaultQueue] addTransactionObserver:self];

}


- (void)requestInAppPurchaseData
{
 NSSet *productIdentifiers = [NSSet setWithObject:kInAppPurchaseCreditProductId];

    productsRequest = [[SKProductsRequest alloc] initWithProductIdentifiers:productIdentifiers];
    productsRequest.delegate = self;
    [productsRequest start];

    // we will release the request object in the delegate callback
}



- (void)productsRequest:(SKProductsRequest *)request didReceiveResponse:(SKProductsResponse *)response
{

    NSArray *products = response.products;


    productID = [products count] == 1 ? [[products objectAtIndex:0] retain] : nil;
    if (productID)
    {
  /*
   NSLog(@"Product title: %@" , productID.localizedTitle);
   NSLog(@"Product description: %@" , productID.localizedDescription);
   NSLog(@"Product price: %@" , productID.price);
   NSLog(@"Product id: %@" , productID.productIdentifier);
   */

  NSUserDefaults *standardUserDefaults = [NSUserDefaults standardUserDefaults];
  NSString *currentCredits = ([standardUserDefaults objectForKey:@"currentCredits"]) ? [standardUserDefaults objectForKey:@"currentCredits"] : @"0";

  testLabel.text = [NSString stringWithFormat:@"%@", currentCredits];
    }

    for (NSString *invalidProductId in response.invalidProductIdentifiers)
    {
        //NSLog(@"Invalid product id: %@" , invalidProductId);
  testLabel.text = @"Try Again Later.";
    }

    // finally release the reqest we alloc/init’ed in requestProUpgradeProductData
    [productsRequest release];

    [[NSNotificationCenter defaultCenter] postNotificationName:kInAppPurchaseManagerProductsFetchedNotification object:self userInfo:nil];

 [self performSelectorOnMainThread:@selector(purchaseCredit) withObject:nil waitUntilDone:NO];
}


//
// call this before making a purchase
//
- (BOOL)canMakePurchases
{
    return [SKPaymentQueue canMakePayments];
}

//
// kick off the upgrade transaction
//
- (void)purchaseCredit
{

    SKPayment *payment = [SKPayment paymentWithProductIdentifier:kInAppPurchaseCreditProductId];

 // *********************************************************************************************************
 [[SKPaymentQueue defaultQueue] addPayment:payment]; // <--- This is where the NSZombie Appears *************
 // *********************************************************************************************************

}

#pragma -
#pragma Purchase helpers

//
// saves a record of the transaction by storing the receipt to disk
//
- (void)recordTransaction:(SKPaymentTransaction *)transaction
{
 if ([transaction.payment.productIdentifier isEqualToString:kInAppPurchaseCreditProductId])
    {
        // save the transaction receipt to disk
        [[NSUserDefaults standardUserDefaults] setValue:transaction.transactionReceipt forKey:@"InAppPurchaseTransactionReceipt" ];
        [[NSUserDefaults standardUserDefaults] synchronize];
    }

}

//
// enable pro features
//
- (void)provideContent:(NSString *)productId
{
 if ([productId isEqualToString:kInAppPurchaseCreditProductId])
    {        
  // Increment currentCredits
  NSUserDefaults *standardUserDefaults = [NSUserDefaults standardUserDefaults];
  NSString *currentCredits = [standardUserDefaults objectForKey:@"currentCredits"];
  int newCreditCount = [currentCredits intValue] + 1;
  [standardUserDefaults setObject:[NSString stringWithFormat:@"%d", newCreditCount] forKey:@"currentCredits"];

  testLabel.text = [NSString stringWithFormat:@"%d", newCreditCount];

    }

}

//
// removes the transaction from the queue and posts a notification with the transaction result
//
- (void)finishTransaction:(SKPaymentTransaction *)transaction wasSuccessful:(BOOL)wasSuccessful
{

    // remove the transaction from the payment queue.
    [[SKPaymentQueue defaultQueue] finishTransaction:transaction];

    NSDictionary *userInfo = [NSDictionary dictionaryWithObjectsAndKeys:transaction, @"transaction" , nil];
    if (wasSuccessful)
    {
        // send out a notification that we’ve finished the transaction
        [[NSNotificationCenter defaultCenter] postNotificationName:kInAppPurchaseManagerTransactionSucceededNotification object:self userInfo:userInfo];
    }
    else
    {
        // send out a notification for the failed transaction
        [[NSNotificationCenter defaultCenter] postNotificationName:kInAppPurchaseManagerTransactionFailedNotification object:self userInfo:userInfo];
    }


 [self updateButtonStatus:@"ON"];

}

//
// called when the transaction was successful
//
- (void)completeTransaction:(SKPaymentTransaction *)transaction
{

 [self updateButtonStatus:@"OFF"];

 [self recordTransaction:transaction];
    [self provideContent:transaction.payment.productIdentifier];
 [self finishTransaction:transaction wasSuccessful:YES];

}

//
// called when a transaction has been restored and and successfully completed
//
- (void)restoreTransaction:(SKPaymentTransaction *)transaction
{
    [self recordTransaction:transaction.originalTransaction];
    [self provideContent:transaction.originalTransaction.payment.productIdentifier];
    [self finishTransaction:transaction wasSuccessful:YES];
}

//
// called when a transaction has failed
//
- (void)failedTransaction:(SKPaymentTransaction *)transaction
{

    if (transaction.error.code != SKErrorPaymentCancelled)
    {
   // error!
        [self finishTransaction:transaction wasSuccessful:NO];
    }
    else
    {
   // this is fine, the user just cancelled, so don’t notify
        [[SKPaymentQueue defaultQueue] finishTransaction:transaction];
    }

 [self updateButtonStatus:@"ON"];

}

#pragma mark -
#pragma mark SKPaymentTransactionObserver methods

//
// called when the transaction status is updated
//
- (void)paymentQueue:(SKPaymentQueue *)queue updatedTransactions:(NSArray *)transactions
{

    for (SKPaymentTransaction *transaction in transactions)
    {
        switch (transaction.transactionState)
        {
            case SKPaymentTransactionStatePurchased:
                [self completeTransaction:transaction];
                break;
            case SKPaymentTransactionStateFailed:
                [self failedTransaction:transaction];
                break;
            case SKPaymentTransactionStateRestored:
                [self restoreTransaction:transaction];
                break;
            default:
                break;
        }
    }
}


@end

Answer 1

I think observers added using addTransactionObserver are apparently weak references - not strong ones, which would explain this. I've made a simple test:

// bad code below:
// the reference is weak so the observer is immediately destroyed
addTransactionObserver([[MyObserver alloc] init]);
...
[[SKPaymentQueue defaultQueue] addPayment:payment]; // crash

And got the same crash even without calling removeTransactionObserver. The solution in my case was to simply keep a strong reference to the observer:

@property (strong) MyObserver* observer;
....
self.observer = [[MyObserver alloc] init];
addTransactionObserver(observer);

Answer 2

The error message indicates a message is being sent to a deallocated instance of InAppPurchaseManager, which is your class. And it's happening after you open the view (creating an instance), close the view (releasing an instance), then opening the view again (creating a second instance). And the problem is happening within the addPayment: call. This indicates that the framework still has a handle on your old, released instance, and is trying to send it a message.

You give the framework a handle to your object in loadStore, when you call

[[SKPaymentQueue defaultQueue] addTransactionObserver:self];

I don't see anywhere where you remove self as an observer. Objects that send out notifications usually do not retain their observers, since doing so can create a retain cycle and/or a memory leak.

In your dealloc code you need to cleanup and call removeTransactionObserver:. That should solve your problem.