Checking Changes That Do Not Show Up

When switching between the device and the simulator, sometimes Xcode does not know whether or not it has built something. To force it to rebuild everything, choose the Build, Clean menu item ( - -K), and rebuild. If this menu item is grayed out, Xcode thinks the app is running. If it is not running, you can force a rebuild by deleting the build directory in your application project folder and rebuilding.