Update your apps to use new features, and test your apps against API changes
Xcode 11.3.1 supports developing apps for iOS 13.3, iPadOS 13.3, tvOS 13.3, watchOS 6.1, and macOS Catalina 10.15.2. Xcode 11.3.1 supports on-device debugging for iOS 8 and later, tvOS 9 and later, and watchOS 2 and later. Xcode 11.3.1 requires a Mac running macOS Mojave 10.14.4 or later.
When you create an Objective-C category file by choosing File > New > File, the newly created file includes an import of the AppKit framework. This causes a compilation error for iOS, tvOS, and watchOS. (55977950) (FB7346800)
Workaround: Remove the import of AppKit from the source file.
Inspection of global variables in Swift and Objective-C works properly in
Fixed a crash that could occur when using an attributed string in a
UILabel. (55737956, 57990674)
Fixed a crash that could occur after dragging a toolbar item out of the Allowed set in the canvas. (18133890, 57982132)
Fixed an issue that would cause Xcode to time out waiting for Simulator.app to become ready, when multiple copies of Xcode are installed. (57050823, 57676897)
Resolved an issue that prevented Xcode from launching processes with Thread Sanitizer enabled on macOS Catalina 10.15.2. (57822138)
Fixed a crash that could occur when typing a doc comment after invoking undo. (56522994, 57762965)
Reduced the size of dependency files (
.d) produced by the Swift compiler, which can improve incremental build times and disk usage for targets with many source files. (57361722, 57865813)