So you are humming along on your new Swift app, and all of a sudden, when you bring in a framework revision or try to deploy to a device, you suddenly start getting dyld: Library not loaded messages when the app tries to launch.
Most likely, the reason for this is that the setting for embedding the Swift standard libraries is turned off, and the app for some reason needs them. The fix is easy enough, just go into your build settings for your app and look for “Always Embed Standard Swift Libraries”. Turn this setting on for your app’s target, clean, and then try to run again.
BTW, Happy 20th Anniversary to the iMac, which was announced to the world by former Apple CEO Steve Jobs on this date in 1998. I have had a few iMacs through the years, and they are great machines.