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 could follow these steps:
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 choose Show Package Contents,
Navigate to Contents->Developer->Platforms->iPhoneOS.platform->DeviceSupport,
Then paste the file you downlaod in it. Other resource.