iOS APNS: sending the device token to the provider in string format

Question

I need to send the APNS device token of my iOS app to my provider by calling a service that expects JSON data in my request. I'm reading Apple's Local and Push Notification Programming Guide and it only says that the application:didRegisterForRemoteNotificationsWithDeviceToken: delegate method passes the device token as NSData and you should pass it to your provider encoded in binary data. But I need it to be converted to string in order to be able to send a JSON request to my provider.

I've also been reading several posts related to this, since it looks it is a common scenario, but I've found some different ways to convert such device token to string to send it, and I'm not sure which of them should be the most appropriate. Which would the most reliable way to deal with this be? I suppose my provider will need to convert this string back to call APNS, and I also need to store this token in the app in order to safely compare it with the new value if a new token is generated and application:didRegisterForRemoteNotificationsWithDeviceToken: is called, to send the token only if it has changed.

Thanks

Answer 1

You are right that you have to convert the device token from NSData to NSString to be able to send it with a JSON object. But what conversion method you choose is completely up to you or the requirements of the provider. The most common methods are a hex string (see for example Best way to serialize an NSData into a hexadeximal string) or a Base64 string (using base64EncodedStringWithOptions). Both are 100% "reliable".

Also you should always send the device token to the provider and not only when it has changed. The provider has to keep a database of all device tokens with a timestamp of when it was sent last recently, in order to compare the timestamp with a possible response from the "feedback service".

Answer 2

In didFinishLaunchingWithOptions method

if ([[[UIDevice currentDevice] systemVersion] floatValue] >= 8.0)
{
    [[UIApplication sharedApplication] registerUserNotificationSettings:[UIUserNotificationSettings settingsForTypes:(UIUserNotificationTypeSound | UIUserNotificationTypeAlert | UIUserNotificationTypeBadge) categories:nil]];
    [[UIApplication sharedApplication] registerForRemoteNotifications];
}
else
{
    [[UIApplication sharedApplication] registerForRemoteNotificationTypes:
     (UIRemoteNotificationTypeBadge | UIRemoteNotificationTypeSound | UIRemoteNotificationTypeAlert)];
}

After doing above lines of code ,add the method below

#pragma mark Push Notifications
- (void)application:(UIApplication *)app didRegisterForRemoteNotificationsWithDeviceToken:(NSData *)deviceToken
{
NSString  *token_string = [[[[deviceToken description]    stringByReplacingOccurrencesOfString:@"<"withString:@""]
                        stringByReplacingOccurrencesOfString:@">" withString:@""]
                       stringByReplacingOccurrencesOfString: @" " withString: @""];
NSString* strURL = [NSString stringWithFormat:@"http://www.sample.com?device_token=%@&type=IOS",token_string];
strURL=[strURL stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding];
NSLog(@"%@",strURL);
NSData *fileData = [NSData dataWithContentsOfURL:[NSURL URLWithString:strURL]];
NSLog(@"content---%@", fileData);
}

After the above listed steps you can use this delegate function to retrieve and handle push notification once it comes.The below added method will fire either the app is running in background or not.The method given below is available from ios7.0

- (void)application:(UIApplication *)application didReceiveRemoteNotification:(NSDictionary *)userInfo fetchCompletionHandler:(void (^)(UIBackgroundFetchResult result))handler

Answer 3

const unsigned *tokenBytes = [deviceToken bytes];
NSString *hexToken = [NSString stringWithFormat:@"%08x%08x%08x%08x%08x%08x%08x%08x",
                      ntohl(tokenBytes[0]), ntohl(tokenBytes[1]), ntohl(tokenBytes[2]),
                      ntohl(tokenBytes[3]), ntohl(tokenBytes[4]), ntohl(tokenBytes[5]),
                      ntohl(tokenBytes[6]), ntohl(tokenBytes[7])];

Converting data to bytes means we can count it. Removing spaces and <> is really not a good idea

Answer 4

- (void)application:(UIApplication *)app didRegisterForRemoteNotificationsWithDeviceToken:(NSData *)_deviceToken {

NSString *str = [NSString stringWithFormat:@"%@",_deviceToken];
//replace '<' and '>' along with spaces before you send it to the server.
}

this has worked reliably for me on almost all web platforms.