Swift Sdtlib tool error: Task failed with exit code 1

Question

So randomly after several hours of work this morning on my app, Xcode just stopped letting me test my app on my iPhone. But I can still test it in the simulator.

Now

Answer 1

I use macOS High Sierra, Xcode 9.3: This worked for me.

1. Go to /Users/JohnAppleseed/Library/Developer/Xcode/DerivedData/
2. Moved all the files to Trash, empty the trash
3. Opened Xcode, Clean and Build.

Restarting xcode or macbook, dragging and dropping certificate in the keychain did not work for me.