WWDC19

Table of Contents

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• What’s New in Swift - Tuesday
  • Binary Frameworks
  • Performance
  • Swift Tooling and Open Source
  • Language and Standard Library

What’s New in Swift - Tuesday

Session materials: https://developer.apple.com/videos/play/wwdc2019/402/

Binary Frameworks

• Module + ABI Stability = Binary frameworks
  • This allows working with modules compiled in a different compiler than another piece of source code

Performance

• Reducing swift runtime overhead with shared runtime to %0 when the code is compiled with Swift 5
• %10 smaller code size, %15 when Optimize for size is being used
• Faster bridging between Swift and Objective-C
• Faster NSDictionary to Dictionary bridging
• 15x faster NSString operations when performed on bridged NSStrings
• Native Swift Strings now interoperate with C APIs without overhead. This is possible by moving to UTF-8 from UTF-16.

Swift Tooling and Open Source

• sourcekitd SourceKit stress tester to reproduce some known sourcekit crashes

Language and Standard Library

• Implicit return from a single expression
• Synthesized default parameters for structs. Ability to construct with selected default parameters only
• String interpolation is 1.7x faster than Swift 4.2
  • Possibility to use interpolation while localizing a string as well
• Opaques result types, to return same concrete types of an instance but hiding them via a protocol to not expose API details to the outside
  • var shape: some Shape { }
  • Only possible with the new Swift 5.1
• Property Wrappers!
  • There are property implementation patterns that come up repeatedly. Rather than hardcode a fixed set of patterns into the compiler, we should provide a general “property wrapper” mechanism to allow these patterns to be defined as libraries.
  • https://github.com/DougGregor/swift-evolution/blob/property-wrappers/proposals/0258-property-wrappers.md
• Define embedded DSLs in Swift to support DSLs with custom DSL builders
  • The compiler recognizes the DSL code