Xcode fails app install after iOS8.4 and Xcode 6.4 updates

Question

Out of nothing my app won't install on my test device (iPhone 6 on 8.4) anymore. I get a message saying "App installation failed. An unknown error has occurred". I updated today to iOS 8.4 and Xcode 6.4 could this have something to do with it?

App still runs on the simulator. Also if I change the name of the top folder I don't get the error and it works fine. Is there some path that I need to change and I am missing?

Answer 1

This is now happening to me daily. The fix I've found is to clean the build folder. To clean the build folder, go to the product menu and hold down the option key. The "Clean" option will change to "Clean Build Folder."

If that doesn't work, then clean the derived data folder. Window -> Projects -> Select your Project -> Delete derived data folder.

As a last resort, you can delete and reinstall the app.