ios註冊遠程推送通知

    ios8之後，ios遠程推送的註冊方式發生了變化：

ios8之前：

[[UIApplication sharedApplication] registerForRemoteNotificationTypes:(UIRemoteNotificationTypeAlert | UIRemoteNotificationTypeBadge | UIRemoteNotificationTypeSound)];

ios8之後：

UIUserNotificationSettings *settings = [UIUserNotificationSettings settingsForTypes:(UIRemoteNotificationTypeBadge
                                                                                             |UIRemoteNotificationTypeSound
                                                                                             |UIRemoteNotificationTypeAlert)
                                                                                 categories:nil];
        [[UIApplication sharedApplication] registerUserNotificationSettings:settings];
        [[UIApplication sharedApplication] registerForRemoteNotifications];

因此，ios8以後代碼中要作區分處理：

if ([[UIApplication sharedApplication] respondsToSelector:@selector(isRegisteredForRemoteNotifications)]) {
        UIUserNotificationSettings *settings = [UIUserNotificationSettings settingsForTypes:(UIRemoteNotificationTypeBadge
                                                                                             |UIRemoteNotificationTypeSound
                                                                                             |UIRemoteNotificationTypeAlert)
                                                                                 categories:nil];
        [[UIApplication sharedApplication] registerUserNotificationSettings:settings];
        [[UIApplication sharedApplication] registerForRemoteNotifications];
    } else {
        [[UIApplication sharedApplication] registerForRemoteNotificationTypes:(UIRemoteNotificationTypeBadge
                                                         |UIRemoteNotificationTypeSound
                                                         |UIRemoteNotificationTypeAlert)];
    }

不然，在ios8的系統上會出現問題。