The file "xxx.xcuserdatad" could not be unlocked. Could not add write permission to the file because you do not own it. Try modifying the permission of the file in the Finder or Terminal. 해결!

The file "xxx.xcuserdatad" could not be unlocked. Could not add write permission to the file because you do not own it. Try modifying the permission of the file in the Finder or Terminal.

분명 난 사용자권한을 가지고 있는데 이런 에러가 났다.. 

터미널에, 폴더의 경로 위에서 

sudo chmod -R 774 폴더이름(현재 xcode project가 있는 폴더 이름)

명령어를 치니까 해결되었다 !!!