I've just updated to Xcode 9.4.1 and experienced an issue with the clipboard being cleared randomly.
So I select a text, hit CMD+C, then go to the position I want to paste it, hit CMD+V, but it plays the system alert sound and doesn't paste anything.
Anyone experienced this issue too?
Update
Still remains with Xcode 10.1
Turning off the 'Automatically Sync Pasteboard' option in the Edit menu of the Simulator works for me. I read it in Apple forums
This really helps! Just uncheck the Automatically Sync Pasteboard
Also read in the Apple forums that closing the simulator while working fixes this issue. So if it happens to me I close the simulator and copy-paste works fine from that point forwards.
Haven't tried it yet but I have feeling that Eva's answer is correct in that the simulator is trying to sync your pasteboard.
** Edit **
Can confirm that Eva's answer works and I no longer have this issue when I turn of automatic syncing on the simulator
The accepted answer doesn't work for me. See my comment there. The problem is with the Handoff.
I had the Handoff option enabled in OS X Settings > General.
After unchecking that option, I have the clipboard synced and no simulator freezes.
来源：https://stackoverflow.com/questions/50857133/xcode-clipboard-copy-paste-stuck