iOS14 example on how to use loadProduct() with SKAdNetwork signature support

showAd.m

-(void) openAppInstallRec:(OBRecommendation * _Nonnull)rec inNavController:(UINavigationController * _Nonnull)navController {
    if (@available(iOS 11.3, *)) {
        SKStoreProductViewController *storeViewController = [[SKStoreProductViewController alloc] init];
        NSDictionary *productParameters = [self prepareLoadProductParams:rec];
        
        NSLog(@"loadProductWithParameters: %@", productParameters);
        [storeViewController loadProductWithParameters:productParameters completionBlock:^(BOOL result, NSError * _Nullable error) {
            // result -  true if the product information was successfully loaded, otherwise false.
            NSLog(@"loadProductWithParameters - result: %@, error: %@", result ? @"true" : @"false", [error localizedDescription]);
        }];
        [navController presentViewController:storeViewController animated:YES completion:nil];
    }
}

-(NSDictionary *) prepareLoadProductParams:(OBRecommendation * _Nonnull)rec {
    NSMutableDictionary* productParameters = [[NSMutableDictionary alloc] init];
    
    if (@available(iOS 11.3, *)) {
        [productParameters setObject: rec.skAdNetworkData.iTunesItemId    forKey: SKStoreProductParameterITunesItemIdentifier];
        [productParameters setObject: rec.skAdNetworkData.adNetworkId     forKey: SKStoreProductParameterAdNetworkIdentifier];
        [productParameters setObject: rec.skAdNetworkData.signature       forKey: SKStoreProductParameterAdNetworkAttributionSignature];
        [productParameters setObject:[[NSUUID alloc] initWithUUIDString:rec.skAdNetworkData.nonce] forKey:SKStoreProductParameterAdNetworkNonce];
        // timestamp and campaignId must be valid
        if (rec.skAdNetworkData.timestamp > 0 && [rec.skAdNetworkData.campaignId isKindOfClass: [NSNumber class]]) {
            [productParameters setObject: @(rec.skAdNetworkData.timestamp)                  forKey: SKStoreProductParameterAdNetworkTimestamp];
            [productParameters setObject: @([rec.skAdNetworkData.campaignId intValue])      forKey: SKStoreProductParameterAdNetworkCampaignIdentifier];
        }
        
        
        if (@available(iOS 14, *)) {
            // These product params are only included in SKAdNetwork version 2.0
            if ([rec.skAdNetworkData.skNetworkVersion isEqualToString:@"2.0"]) {
                [productParameters setObject: @"2.0"            forKey: SKStoreProductParameterAdNetworkVersion];
                [productParameters setObject: rec.skAdNetworkData.sourceAppId    forKey: SKStoreProductParameterAdNetworkSourceAppStoreIdentifier];
            }
        }
    } else {
        return nil;
    }
    
    return productParameters;
}