I've created an .icns and set it in the Document Types section of my project, but my documents' icons in Finder remain generic. I've noticed that if I change my document type's file extension, the icon displays. Is there a cache I need to clear or some other way to update the icon without changing the file extension?
To force refresh icon put this into your terminal
/System/Library/Frameworks/ApplicationServices.framework/Frameworks/LaunchServices.framework/Support/lsregister -kill -r -domain local -domain system -domain user; killall Dock
Mavericks:
/System/Library/Frameworks/CoreServices.framework/Versions/A/Frameworks/LaunchServices.framework/Versions/A/Support/lsregister; killall Dock
来源：https://stackoverflow.com/questions/32260870/xcode-document-icon-not-updating