Xcode 8 hangs / unresponsive when opening storyboard

Question

I\'ve recently upgraded to Xcode 8 and updated my project to Swift 3. All worked fine for a little while. Storyboard loading has always been slow (even when still running Xcode

Answer 1

I had this problem shortly after upgrading to Xcode 9, any time I changed anything in the storyboard (even moving a view by 1 px), it would hang with the spinning beachball of death for at least 10s.

I didn't want to clear my entire xcuserdata folder and lose all my breakpoints etc, but just deleting UserInterfaceState.xcuserstate and restarting Xcode worked for me.