次に、.mファイルに次のコードを追加します。この部分は複雑になるので、コード内のコメントを読むことをお勧めします。

//If you have more than one in-app purchase, you can define both of
//of them here. So, for example, you could define both kRemoveAdsProductIdentifier
//and kBuyCurrencyProductIdentifier with their respective product ids
//
//for this example, we will only use one product

#define kRemoveAdsProductIdentifier @"put your product id (the one that we just made in App Store Connect) in here"

- (IBAction)tapsRemoveAds{
    NSLog(@"User requests to remove ads");

    if([SKPaymentQueue canMakePayments]){
        NSLog(@"User can make payments");
    
        //If you have more than one in-app purchase, and would like
        //to have the user purchase a different product, simply define 
        //another function and replace kRemoveAdsProductIdentifier with 
        //the identifier for the other product

        SKProductsRequest *productsRequest = [[SKProductsRequest alloc] initWithProductIdentifiers:[NSSet setWithObject:kRemoveAdsProductIdentifier]];
        productsRequest.delegate = self;
        [productsRequest start];
    
    }
    else{
        NSLog(@"User cannot make payments due to parental controls");
        //this is called the user cannot make payments, most likely due to parental controls
    }
}

- (void)productsRequest:(SKProductsRequest *)request didReceiveResponse:(SKProductsResponse *)response{
    SKProduct *validProduct = nil;
    int count = [response.products count];
    if(count > 0){
        validProduct = [response.products objectAtIndex:0];
        NSLog(@"Products Available!");
        [self purchase:validProduct];
    }
    else if(!validProduct){
        NSLog(@"No products available");
        //this is called if your product id is not valid, this shouldn't be called unless that happens.
    }
}

- (void)purchase:(SKProduct *)product{
    SKPayment *payment = [SKPayment paymentWithProduct:product];

    [[SKPaymentQueue defaultQueue] addTransactionObserver:self];
    [[SKPaymentQueue defaultQueue] addPayment:payment];
}

- (IBAction) restore{
    //this is called when the user restores purchases, you should hook this up to a button
    [[SKPaymentQueue defaultQueue] addTransactionObserver:self];
    [[SKPaymentQueue defaultQueue] restoreCompletedTransactions];
}

- (void) paymentQueueRestoreCompletedTransactionsFinished:(SKPaymentQueue *)queue
{
    NSLog(@"received restored transactions: %i", queue.transactions.count);
    for(SKPaymentTransaction *transaction in queue.transactions){
        if(transaction.transactionState == SKPaymentTransactionStateRestored){
            //called when the user successfully restores a purchase
            NSLog(@"Transaction state -> Restored");

            //if you have more than one in-app purchase product,
            //you restore the correct product for the identifier.
            //For example, you could use
            //if(productID == kRemoveAdsProductIdentifier)
            //to get the product identifier for the
            //restored purchases, you can use
            //
            //NSString *productID = transaction.payment.productIdentifier;
            [self doRemoveAds];
            [[SKPaymentQueue defaultQueue] finishTransaction:transaction];
            break;
        }
    }   
}

- (void)paymentQueue:(SKPaymentQueue *)queue updatedTransactions:(NSArray *)transactions{
    for(SKPaymentTransaction *transaction in transactions){
        //if you have multiple in app purchases in your app,
        //you can get the product identifier of this transaction
        //by using transaction.payment.productIdentifier
        //
        //then, check the identifier against the product IDs
        //that you have defined to check which product the user
        //just purchased            

        switch(transaction.transactionState){
            case SKPaymentTransactionStatePurchasing: NSLog(@"Transaction state -> Purchasing");
                //called when the user is in the process of purchasing, do not add any of your own code here.
                break;
            case SKPaymentTransactionStatePurchased:
            //this is called when the user has successfully purchased the package (Cha-Ching!)
                [self doRemoveAds]; //you can add your code for what you want to happen when the user buys the purchase here, for this tutorial we use removing ads
                [[SKPaymentQueue defaultQueue] finishTransaction:transaction];
                NSLog(@"Transaction state -> Purchased");
                break;
            case SKPaymentTransactionStateRestored:
                NSLog(@"Transaction state -> Restored");
                //add the same code as you did from SKPaymentTransactionStatePurchased here
                [[SKPaymentQueue defaultQueue] finishTransaction:transaction];
                break;
            case SKPaymentTransactionStateFailed:
                //called when the transaction does not finish
                if(transaction.error.code == SKErrorPaymentCancelled){
                    NSLog(@"Transaction state -> Cancelled");
                    //the user cancelled the payment ;(
                }
                [[SKPaymentQueue defaultQueue] finishTransaction:transaction];
                break;
        }
    }
}

- (void)doRemoveAds{
    ADBannerView *banner;
    [banner setAlpha:0];
    areAdsRemoved = YES;
    removeAdsButton.hidden = YES;
    removeAdsButton.enabled = NO;
    [[NSUserDefaults standardUserDefaults] setBool:areAdsRemoved forKey:@"areAdsRemoved"];
    //use NSUserDefaults so that you can load whether or not they bought it
    //it would be better to use KeyChain access, or something more secure
    //to store the user data, because NSUserDefaults can be changed.
    //You're average downloader won't be able to change it very easily, but
    //it's still best to use something more secure than NSUserDefaults.
    //For the purpose of this tutorial, though, we're going to use NSUserDefaults
    [[NSUserDefaults standardUserDefaults] synchronize];
}

- (void)doRemoveAds{
    [self.view setBackgroundColor:[UIColor blueColor]];
    areAdsRemoved = YES
    //set the bool for whether or not they purchased it to YES, you could use your own boolean here, but you would have to declare it in your .h file

    [[NSUserDefaults standardUserDefaults] setBool:areAdsRemoved forKey:@"areAdsRemoved"];
    //use NSUserDefaults so that you can load wether or not they bought it
    [[NSUserDefaults standardUserDefaults] synchronize];
}

areAdsRemoved = [[NSUserDefaults standardUserDefaults] boolForKey:@"areAdsRemoved"];
[[NSUserDefaults standardUserDefaults] synchronize];
//this will load wether or not they bought the in-app purchase

if(areAdsRemoved){
    [self.view setBackgroundColor:[UIColor blueColor]];
    //if they did buy it, set the background to blue, if your using the code above to set the background to blue, if your removing ads, your going to have to make your own code here
}