iOS Device token的問題

Device token for an iPhone device生成之后就永遠(yuǎn)不變嗎？

不是，if a device is wiped (應(yīng)該是重裝系統(tǒng)), it will get a new device token. 

官方網(wǎng)站是這樣寫的： If the user restores backup data to a new device or computer, or reinstalls the operating system, the device token changes

正是因為device有可能改變，所以建議在app start時（即在didFinishLaunchingWithOptions  里）調(diào)用registerForRemoteNotificationTypes來獲取device token以檢查device token是否改變，如果改變了就應(yīng)該把新token傳給push provider。（官方描述：An application should register every time it launches and give its provider the current token）

device token應(yīng)該存儲在NSUserDefaults來達(dá)到新舊比較的目的

那么舊device token在push provider對應(yīng)的record怎么辦？

方案1：把舊device token send to provider and request delete record

方案2：使用apns feedback service。

方案2可能更好些，因為總是需要使用apns feedback service來處理用戶在device里刪除app的情況。

調(diào)用registerForRemoteNotificationTypes方法后，成功注冊后，APNS就會返回一個device token，然后回調(diào)delegate methoddidRegisterForRemoteNotificationsWithDeviceToken, 如果注冊失敗，則回調(diào)delegate method didFailToRegisterForRemoteNotificationsWithError。

注意：

* 在第一次調(diào)用registerForRemoteNotificationTypes方法時沒有聯(lián)網(wǎng)，則既不會調(diào)用didRegisterForRemoteNotificationsWithDeviceToken，也不會調(diào)用didFailToRegisterForRemoteNotificationsWithError

*在第一次調(diào)用registerForRemoteNotificationTypes注冊成功后，之后即使沒有聯(lián)網(wǎng)，再調(diào)用registerForRemoteNotificationTypes時都會以最上一次的device token作為參數(shù)回調(diào)didRegisterForRemoteNotificationsWithDeviceToken方法。

* (官方描述) If your application has previously registered, calling registerForRemoteNotificationTypes: results in the operating system passing the device token to the delegate immediately without incurring additional overhead.

上述東東參考官方網(wǎng)站關(guān)于Registering for Remote Notifications的講解