Error: executable doesn't exist:


I did the BMITime exercise for this chapter. Everything went fine. A couple of days later, I went back and re-did the exercise-- creating a new project and starting from scratch.

At some point I made an error, but I could never get the project to work again. So I deleted all of my classes from the new project and copied my classes in from the working project. I did a clean and a Build. Build succeeds. However, when I run, I get this error in the output :

error: executable doesn’t exist: '/Users/theStig/Library/Developer/Xcode/DerivedData/BMITime3-fqvgnssynudogoavjlsxinleazzv/Build/Products/Debug/BMITime3’
error: failed to launch ‘/Users/theStig/Library/Developer/Xcode/DerivedData/BMITime3-fqvgnssynudogoavjlsxinleazzv/Build/Products/Debug/BMITime3’ – SBTarget is invaliderror: failed to launch ‘/Users/theStig/Library/Developer/Xcode/DerivedData/BMITime3-fqvgnssynudogoavjlsxinleazzv/Build/Products/Debug/BMITime3’ – SBTarget is invalid

What is going on?