summarize what's new in Xcode

What's New in Xcode 16

Xcode 16 introduces several exciting features and improvements across various aspects of app development:

1. Code Completion: Xcode 16 features an innovative new engine for code completion, powered by a model specifically trained for Swift and Apple SDKs. This engine uses your project symbols to customize suggestions and runs locally on your Mac, ensuring privacy and fast results. It even works offline.

2. Swift 6: A new language mode in Swift 6 provides concurrency safety guarantees, turning data races into compile-time issues, which improves code correctness and safety.

3. Previews: Xcode Previews now have a dynamic linking architecture that uses the same build artifacts for both previews and when you build and run, avoiding unnecessary rebuilds. A new previewable macro allows dynamic properties like state to be used directly in previews, reducing code overhead.

4. Builds: Xcode 16 introduces explicit modules, which improve parallelism, diagnostics, and debugging without changing code. For C and Objective-C, explicit modules are on by default, while Swift requires opting in.

5. Debugging and Performance: The thread performance checker now includes diagnostics for excessive disk writes and slow app launches. The organizer provides insights into app performance, helping prioritize issues with the greatest impact.

6. Instruments and Flame Graphs: New features in Instruments, including flame graphs, help visualize call stacks and identify performance issues.

7. SwiftAssist: A new tool, SwiftAssist, acts as a coding companion, leveraging a powerful model that runs in the cloud to assist with coding tasks.

For more detailed insights, you can explore the session What’s new in Xcode 16 and Platforms State of the Union.