Error:
2019-11-24 22:16:01.047997+0800 SingleViewDemo[22576:34699748] Unknown class FeedbackCell in Interface Builder file.
2019-11-24 22:16:01.058953+0800 SingleViewDemo[22576:34699748] *** Terminating app due to uncaught exception 'NSUnknownKeyException', reason: '[<UITableViewCell 0x7fba6c029a00> setValue:forUndefinedKey:]: this class is not key value coding-compliant for the key checkoutButton.'
解决方法：
1. 先查看xib的Connections是否有失效，有的话重新设置connections
2. 如果方法一无效，尝试勾选Identity inspector的"Inherit Module From Target"选项
