invalid nib registered for identifier（friendCell）- nib must contain exactly one top level object which must be a UITableViewCell instance
通过xib创建cell的时候如果cell中放的有与cell同级的控件。当运行程序的时候就会报这个错误。
Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'invalid nib registered for identifier (friendCell) - nib must contain exactly one top level object which must be a UITableViewCell instance
解决办法就将与cell同级的多余的控件删除。保证xib中Cell的唯一性就可以了。