获取设备推送权限

// Before iOS 8:
- (BOOL)application:(UIApplication *)application
didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
    ...
    // Register for push notifications
    [application registerForRemoteNotificationTypes:
                                UIRemoteNotificationTypeBadge |
                                UIRemoteNotificationTypeAlert |
                                UIRemoteNotificationTypeSound];
    ...
}

//For iOS 8:
- (BOOL)application:(UIApplication *)application
didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
    ...
    UIUserNotificationSettings *settings = [UIUserNotificationSettings settingsForTypes:UIUserNotificationTypeAlert
                                            | UIUserNotificationTypeBadge
                                            | UIUserNotificationTypeSound
                                                                             categories:nil];
    [application registerUserNotificationSettings:settings];
    [application registerForRemoteNotifications];
    ...
}