I am having the same problem ever since updating Xcode yesterday. Here's my diagnostics screen: ---------------------------------------- CompileDylibError: Failed to build ContentView.swift Compiling failed: file '/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneSimulator.platform/Developer/SDKs/iPhoneSimulator15.2.sdk/usr/lib/swift/shims/Visibility.h' has been modified since the module file '/var/folders/jt/s96c8fv518s_1y_6925ml4sc0000gn/C/clang/ModuleCache/108X1IN8WGNX1/SwiftShims-2TTN5UXQBRCCQ.pcm' was built: mtime changed <unknown>:0: error: file '/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneSimulator.platform/Developer/SDKs/iPhoneSimulator15.2.sdk/usr/lib/swift/shims/Visibility.h' has been modified since the module file '/var/folders/jt/s96c8fv518s_1y_6925ml4sc0000gn/C/clang/ModuleCache/108X1IN8WGNX1/SwiftShims-2TTN5UXQBRCCQ.pcm' was built: mtime changed <unknown>:0: note: please rebuild precompiled header '/var/folders/jt/s96c8fv518s_1y_6925ml4sc0000gn/C/clang/ModuleCache/108X1IN8WGNX1/SwiftShims-2TTN5UXQBRCCQ.pcm' <module-includes>:1:9: note: in file included from <module-includes>:1: #import "LibcOverlayShims.h"         ^ /Applications/Xcode.app/Contents/Developer/Platforms/iPhoneSimulator.platform/Developer/SDKs/iPhoneSimulator15.2.sdk/usr/lib/swift/shims/LibcOverlayShims.h:21:2: error: file '/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneSimulator.platform/Developer/SDKs/iPhoneSimulator15.2.sdk/usr/lib/swift/shims/Visibility.h' has been modified since the module file '/var/folders/jt/s96c8fv518s_1y_6925ml4sc0000gn/C/clang/ModuleCache/108X1IN8WGNX1/SwiftShims-2TTN5UXQBRCCQ.pcm' was built: mtime changed #include "Visibility.h"  ^ /Applications/Xcode.app/Contents/Developer/Platforms/iPhoneSimulator.platform/Developer/SDKs/iPhoneSimulator15.2.sdk/usr/lib/swift/shims/LibcOverlayShims.h:21:2: note: please rebuild precompiled header '/var/folders/jt/s96c8fv518s_1y_6925ml4sc0000gn/C/clang/ModuleCache/108X1IN8WGNX1/SwiftShims-2TTN5UXQBRCCQ.pcm' #include "Visibility.h"  ^ <unknown>:0: error: missing required module 'SwiftOverlayShims' ================================== |  BuildInvocationError |   |  /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/swiftc -F /Applications/Xcode.app/Contents/SharedFrameworks-iphonesimulator -enforce-exclusivity=checked -DDEBUG -sdk /Applications/Xcode.app/Contents/Developer/Platforms/iPhoneSimulator.platform/Developer/SDKs/iPhoneSimulator15.2.sdk -target arm64-apple-ios14.0-simulator -Xfrontend -serialize-debugging-options -enable-testing -swift-version 5 -I /Users/danuff/Library/Developer/Xcode/DerivedData/CAI-fpvdurwckhlgpoczgdolkzdvwcyr/Build/Intermediates.noindex/Previews/CAI/Products/Debug-iphonesimulator -F /Users/danuff/Library/Developer/Xcode/DerivedData/CAI-fpvdurwckhlgpoczgdolkzdvwcyr/Build/Intermediates.noindex/Previews/CAI/Products/Debug-iphonesimulator -c -j8 -serialize-diagnostics -Xcc -I/Users/danuff/Library/Developer/Xcode/DerivedData/CAI-fpvdurwckhlgpoczgdolkzdvwcyr/Build/Intermediates.noindex/Previews/CAI/Intermediates.noindex/CAI.build/Debug-iphonesimulator/CAI.build/swift-overrides.hmap -Xcc -iquote -Xcc /Users/danuff/Library/Developer/Xcode/DerivedData/CAI-fpvdurwckhlgpoczgdolkzdvwcyr/Build/Intermediates.noindex/Previews/CAI/Intermediates.noindex/CAI.build/Debug-iphonesimulator/CAI.build/CAI-generated-files.hmap -Xcc -I/Users/danuff/Library/Developer/Xcode/DerivedData/CAI-fpvdurwckhlgpoczgdolkzdvwcyr/Build/Intermediates.noindex/Previews/CAI/Intermediates.noindex/CAI.build/Debug-iphonesimulator/CAI.build/CAI-own-target-headers.hmap -Xcc -I/Users/danuff/Library/Developer/Xcode/DerivedData/CAI-fpvdurwckhlgpoczgdolkzdvwcyr/Build/Intermediates.noindex/Previews/CAI/Intermediates.noindex/CAI.build/Debug-iphonesimulator/CAI.build/CAI-all-target-headers.hmap -Xcc -iquote -Xcc /Users/danuff/Library/Developer/Xcode/DerivedData/CAI-fpvdurwckhlgpoczgdolkzdvwcyr/Build/Intermediates.noindex/Previews/CAI/Intermediates.noindex/CAI.build/Debug-iphonesimulator/CAI.build/CAI-project-headers.hmap -Xcc -I/Users/danuff/Library/Developer/Xcode/DerivedData/CAI-fpvdurwckhlgpoczgdolkzdvwcyr/Build/Intermediates.noindex/Previews/CAI/Products/Debug-iphonesimulator/include -Xcc -I/Users/danuff/Library/Developer/Xcode/DerivedData/CAI-fpvdurwckhlgpoczgdolkzdvwcyr/Build/Intermediates.noindex/Previews/CAI/Intermediates.noindex/CAI.build/Debug-iphonesimulator/CAI.build/DerivedSources-normal/arm64 -Xcc -I/Users/danuff/Library/Developer/Xcode/DerivedData/CAI-fpvdurwckhlgpoczgdolkzdvwcyr/Build/Intermediates.noindex/Previews/CAI/Intermediates.noindex/CAI.build/Debug-iphonesimulator/CAI.build/DerivedSources/arm64 -Xcc -I/Users/danuff/Library/Developer/Xcode/DerivedData/CAI-fpvdurwckhlgpoczgdolkzdvwcyr/Build/Intermediates.noindex/Previews/CAI/Intermediates.noindex/CAI.build/Debug-iphonesimulator/CAI.build/DerivedSources -Xcc -DDEBUG=1 -working-directory "/Users/danuff/Documents/CPS/iOS/iOS 15/Projects (Current)/iPhone : iPad/SwiftUI/General/CAI" /Users/danuff/Library/Developer/Xcode/DerivedData/CAI-fpvdurwckhlgpoczgdolkzdvwcyr/Build/Intermediates.noindex/Previews/CAI/Intermediates.noindex/CAI.build/Debug-iphonesimulator/CAI.build/Objects-normal/arm64/ContentView.1.preview-thunk.swift -o /Users/danuff/Library/Developer/Xcode/DerivedData/CAI-fpvdurwckhlgpoczgdolkzdvwcyr/Build/Intermediates.noindex/Previews/CAI/Intermediates.noindex/CAI.build/Debug-iphonesimulator/CAI.build/Objects-normal/arm64/ContentView.1.preview-thunk.o -module-name CAI_PreviewReplacement_ContentView_1 -Onone -Xfrontend -disable-modules-validate-system-headers -gline-tables-only

Hi, The image above looks too much like an iPhone. You'll have to change the image.

This happens to me quite often. Here's what I do: Shut down Xcode. Unplug iOS device from computer. Reboot. Plug iOS device back in. Start Xcode. Clean project. Try again. If it still doesn't work, do the above again, BUT also reboot the iOS device.

Yes, I do all the time and there are some awesome ones. Here's a good start: https://github.com/public-apis/public-apis Dan

This happens to me sometimes. What I do is: Quit Xcode. Reload Xcode and the project. If it happens again, do 1 and 2 above, reboot the computer, and try again. Hope this helps, Dan Uff

There is a hack that allows someone to show a message on the login screen, and maybe he/she just put it there to scare the pants off of you. Do an internet search for how to add a message to the login screen and get rid of it. Besides, if the NSA was monitoring you, why would they TELL you? Dan Uff

Would you have any idea why this is happening to ME?

The way I understand it, they are only to be used in code. Also, if you use an Apple-specific symbol (such as the iCloud symbol) it can only be used as a representation of an iCloud function. Dan Uff

All I did was, make the new app and used the same Bundle Identifier inside the new app. I then made a pop-up (that would only come up once) explaining the new (designed) app. Less confusion for the end user. Which, in my experience, they don't take too likely when they have to download another app and re-pay for some of the same functionality. Dan Uff

Hi, If you're using storyboards, it means you don't have that IBOutlet connected to an object (such as a label, text, etc) in the storyboard. Hope this helps, Dan Uff

Hi, I too have had problems with the master/detail view of Swift and SwiftUI. But the below video has helped me a great deal. https://youtu.be/nA6Jo6YnL9g Hope this helps.

How I read the WeatherKit docs., the  Weather Logo must come from the attribution URL, and be on the main view controller period. No other way to do it. But I am even having problems getting that far. Dan Uff

I've figured it out. Thanks.

Logon to YouTube. There are plenty of videos on the correct way to do JSON in Swift. [https://www.youtube.com/results?search_query=json+and+swift)

Try this: Close Xcode. Reboot the Mac. Reload Xcode. Reload project. BUT before trying to run it, clear project files. If it still shows red files, look for those files manually in the Finder or recreate them. Dan Uff