[objective-c]推送警告处理

在使用iOS推送时，出现下面错误：

**[1412:60b] You've implemented -[<UIApplicationDelegate> application:performFetchWithCompletionHandler:], but you still need to
add "fetch" to the list of your supported UIBackgroundModes in your Info.plist.

**[1412:60b] You've implemented -[<UIApplicationDelegate> application:didReceiveRemoteNotification:fetchCompletionHandler:],
 but you still need to add "remote-notification" to the list of your supported UIBackgroundModes in your Info.plist.

解决方法：PORJECT --> Capabilities --> Background Modes --> Background fetch & Remote notifications -->选中为on 状态