Found myself with something of a head-scratcher today. After pulling some changes from an iOS project, I fired it up in XCode only to get an error:

Property <property name> not found on object of type __strong <object type>

I carefully scanned the offending line for typos and couldn't see anything amiss. I tried a Clean of the build, seeing the same error on rebuilding. Since the class in question was in a file imported through CocoaPods, I tried rebuilding the Pod project, but still got the same error.

I wondered if there might be a duplicated name somewhere, so I tried Option+clicking on the protocol name where I found the error. This took me to the header where I expected the property would be missing, but, surprisingly it was right there.

Apparently, running Clean on the build didn't actually clean everything up.

After searching around a bit, I came across a StackOverflow post from a few years relating to clearing caches for xibs, so I tried deleting everything under:

~/Library/Developer/Xcode/DerivedData

I hit build again, and bingo! No more annoying error. Thanks to matt for getting me out of an annoying tight spot!