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

ios apple-push-notifications string-formatting devicetoken
AppsDev picture AppsDev · Apr 5, 2014 · Viewed 17.4k times · Source

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

Martin R picture Martin R · Apr 5, 2014

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".

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