New in Swift iOS 13

Improved Performance

• 0% Launch time overhead with Swift 5
• 15% Smaller Code Size when using ‘Optimize for Size’
• Faster Bridging Between Swift and Objective-C. Improved string interoperability. 1.6X faster NSDictionary to Dictionary Bridging. 15X faster NSString operations when performed on bridged Swift Strings.

SwiftUI

• Build user interfaces across all Apple platforms
• Improved LocalizedString Interpolation. SwiftUI supports formatted LocalizedString better

More info:
https://developer.apple.com/videos/play/wwdc2019/402/