问题描述：今天在做TAG App 时在Project上不小心“New Group from Selection” 了下。然后无法撤销了。。。Project上就一直顶着一个New Group。
问题解决：
- close xcode
- right click on your project's .xcodeproj, then click "Show Package Contents"
- inside .xcodeproj, remove the project.xcworkspace
- save it and re-open your xcode project and it would be rebuild the file
