After releasing the iOS 11.3, tvOS 11.3, and watchOS 4.3 software updates for supported iPhone, iPad, iPod touch, Apple TV, and Apple Watch devices, Apple also released the final Xcode 9.3 IDE for application developers.
Xcode 9.3 has been in development as part of Apple's iOS 11.3, tvOS 11.3, macOS High Sierra 10.13.4, and watchOS 4.3 software updates, for which it includes up-to-date SDKs (Software Development Kits) designed for developers who want to design and build apps for the iOS, macOS, tvOS, and watchOS operating systems.
Highlights of the Xcode 9.3 release include a new Energy tab in the Organizer window that shows you information about how much power your app consumes, support for running Swift build tasks and other commands simultaneously to improve build performance, and better support for editing extremely large files with the source editor.
Support for AR Reference Image files, Swift compiler code optimizations
Xcode 9.3 also introduces support for AR Reference Image files to asset catalogs, which can be detected in the real world by your AR (Augmented Reality) apps made with ARKit, a new xccov command-line tool that lets you inspect code coverage reports, and a new code size optimization to the Swift compiler that can be enabled with the -Osize build flag.
Other than that, Xcode 9.3 lets application developers quickly access callers by clicking on a symbol while holding the Command key on their Macs. Of course, there are various smaller improvements and the usual bug fixes that make Xcode a better place for all aspiring iOS, macOS, tvOS, and watchOS application developers.
Xcode 9.3 is now available for all users running a recent macOS release, and can be installed as we speak through the Updates tab of the Mac App Store app on your Mac. Be aware though that it's a hefty update weighing about 5.25GB in size, so it might take a while for it to be downloaded and installed on your computer.