I was running my self-developed software on my iPhone 7 which runs iOS 12.2 when an alert had popped up:
This iPhone 7 (Model 1660, 1778, 1779, 1780) is running iOS 12.2 (16E5201e), which may not be supported by this version of Xcode.
You have to download "device support files for the iOS" from here, And if you need any other "device support files for the iOS" you could download from here, Thin unzip it, Then go to your application folder, Right-click on the Xcode-Beta.app and chooseShow Package Contents, Navigate to Contents->Developer->Platforms->iPhoneOS.platform->DeviceSupport, Then paste the file you downlaod in it. Other resource.
For Xcode Version 10
Copy 12.2 (16E226) directory to Applications ▸ Xcode.app ▸ Show package Contents ▸ Contents ▸ Developer ▸ Platforms ▸ iPhoneOS.platform ▸ DeviceSupport
Quit Xcode and open again.
=> Update for iOS 12.3 step 1 -> 2 copy folder 12.2 (16E226) and rename 12.3 -> 3
You need Xcode 10.2 which is now available in the Mac AppStore and requires macOS 10.14.4. Direct download is not available right now.
git clone https://github.com/iGhibli/iOS-DeviceSupport.git
cd iOS-DeviceSupport
sudo ./deploy.py -t /Applications/Xcode.app
More detail: https://github.com/iGhibli/iOS-DeviceSupport
If you already have folders from recent versions like below, you can often just duplicate the most recent one and rename it to whatever version Xcode asks for.
Xcode 10.2 beta 3 (current version)
Available for download here:
Depending on your use case, the answer could be different.
If you want DEBUGGING (breakpoint, logging on console...) on your real device iOS 12.2, then you must have Xcode 10.2 (it's beta at this moment)
If you want to RUN your app on your device, you can use Xcode 10.1 (thought even Xcode 9 can do that). You can do that using beta distribution service like TestFlight, Fabric... Or by using Xcode, you can archiving your app, then drag & drop the .app file in your device.
来源：https://stackoverflow.com/questions/54876861/which-version-of-xcode-support-ios-12-2