这个答案已过时且不支持iOS 10，你可以查看此答案。

This answer is outdated and doesn't support on iOS 10, you can check this answer.

使用此代码

let isRegisteredForRemoteNotifications = UIApplication.shared.isRegisteredForRemoteNotifications
if isRegisteredForRemoteNotifications {
     // User is registered for notification
} else {
     // Show alert user is not registered for notification
}