Can't enable spell checker option in Xcode
I believe this is a bug. I am not sure if it has been fixed. Try make sure you’re on the latest Xcode version.

From Stack Overflow:


  I believe this is a duplicate post but I'll answer anyway.
  This is an Xcode bug. There have been radars filed. As far as I am unaware there is no work around or fix currently.


That was posted at a similar time to when this was posted.