https://www.developer-tech.com/news/2019/sep/27/apple-swift-ios-13-it-shifts-objective-c/

An analysis shows that Apple’s own use of Swift has doubled in iOS 13 as it further distances itself from Objective-C.

First introduced by Apple in 2014, Swift is now the main programming language for development across Cupertino’s platforms. Adoption of Swift by third-party developers is high, but much of Apple’s operating system still uses Objective-C.