If you see this error after updating to Catalina, running
rails c, and then trying to list a few active records:
+[__NSCFConstantString initialize] may have been in progress in another thread when fork() was called. We cannot safely call it or ignore it in the fork() child process. Crashing instead. Set a breakpoint on objc_initializeAfterForkError to debug.
The issue is that spring is doing unsafe threading.
So you can either turn off
Or you can turn off the thread-safety check:
As for me, I’ll turn of the thread-safety check for my development env.
You can find some more discussions on this topic: