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.'
Solution:
1. First check whether xib of Connections has failed, any reset connections
2. If a method is invalid, try checking the Identity inspector of "Inherit Module From Target" option
