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whats-new-xcode-16.md

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What's new in Xcode 16

Presenters:

  • Daisy Hernandez, Xcode Previews Engineer
  • Jake Petroules, Build Experience Manager

Link: https://developer.apple.com/wwdc24/10135

Edit

Code completion

  • More thorough code suggestions
  • On-device coding models specifically trained for Swift and Apple SDKs
  • Available running Xcode 16 on macOS Sequoia

Swift 6

  • New language mode, concurrency stuff
  • Compile-time diagnosis of data race issues
  • Incrementally enable warnings for each upcoming language feature
    • In Build Settings, navigate to "Upcoming" - this shows Swift 6 features
    • You can enable them one-by-one to diagnose and fix issues incrementally

Check out: Migrate your ap to Swift 6

Previews

Two new APIs:

  • @Previewable: macro that can be attached to property wrappers to use them directly in a preview. You don't have to wrap them in container views.
  • PreviewModifier: new protocol that makes it easier to share environments or data for Previews. Enables Preview system to cache data.
    • Use makeSharedContext to asynchronously load data
    • Use body method to wrap preview with shared context
    • Can define an extension on PreviewTrait to use the PreviewModifier at each call site

Build

Explicit modules

  • Improved parallelism

  • Better diagnostics

  • Faster debugging

  • For C/Objective-C: On by default

  • Swift: opt-in

    • In Build Settings, enable "Explicitly Built Modules"

  • In Xcode 16, don't have to wait for SPM to finish loading packages

  • Xcode splits up the processing of each compilation unit into three distinct phases:

    • Scan
    • Build modules
    • Build source

Check out: Demystify explicitly built modules

Debug

  • Faster debugging with explicit modules

  • Smaller, faster debug symbols with DWARF5 on macOS Sequoia and iOS 18

  • Thread performance checker now also adds disk write diagnostics and launch diagnostics

  • New Unified Backtrace view that lets you follow the call stack (icon in bottom bar looks like three stacked horizontal lines)

  • New RealityKit debugger

  • View entities

Check out:

  • Break into the RealityKit debugger
  • Run, break, and inspect: Explore effective debugging in LLDB

Test

Swift Testing

  • New framework uses Swift language features to make testing more powerful and precise
  • Can name function whatever you want, just add the @Test macro
  • Expect macro takes any boolean expression #expect(plant == expected)
  • View results to see values
  • Use Quick Actions (cmd + shift + a) to rerun specific test
  • Provide arguments to a test function
  • Instead of having multiple test functions, have a single test with arguments to test multiple states
  • Tag-based organization to group tests across different suites
    • Extend the Tag type to add a custom tag - i.e.: 
      extension Tag {
    @Tag static var planting: Self
}
    • Add tag to Test macro
    • You can use tags to include or exclude tests from test plans

Check out:

  • Meet Swift Testing
  • Go further with Swift Testing

Profile

Diagnose performance problems with Instruments, which you can access from the Profile action in Xcode

  • You can set a range to look at a portion of the data
  • Use a blame graph to spot issues at a glance
  • Left side of graph always visualizes code that is executed the most
  • Blame graphs work for every instrument that uses call trees

Check out release notes or download Xcode 16 and give it a try!