ios - Is there a similar function to "applicationWillTerminate()", i can use on AppleWatch?

Question

I need to save data in NSUserDefaults before the AppleWatch App will crash. Otherwise the iOS App will think the AppleWatch App is still running and thats not working.

Answer 1

Your underlying goal, I think, is that you want to ensure that the Containing App is aware when its Apple WatchKit App Extension has crashed.

You can achieve this by getting the Watchkit Extension to periodically send out a Darwin Notification which the containing app subscribes to. Then when the containing app does not get a message from the extension within some timeout limit, it knows the WatchKit extension crashed. This is the most lightweight way I know to achieve this.

Another way is to make the WatchKit app extension periodically call:

+ (BOOL)openParentApplication:(NSDictionary *)userInfo
         reply:(void (^)(NSDictionary *replyInfo,
                         NSError *error))reply

It is not as lightweight, but has the advantage of allowing you to supply some dictionary data, such as a timestamp value or sequence number.