SwiftUi under the hood

SwiftUI Under the Hood

At WWDC 2024, Apple provided insights into the inner workings of SwiftUI, highlighting its integration with other frameworks and its capabilities for building user interfaces across platforms.

Key Points:

1. Interoperability with UIKit and AppKit:

   • SwiftUI has been designed to work seamlessly with UIKit and AppKit, allowing developers to use views from these frameworks within SwiftUI. This is achieved through protocols like UIViewRepresentable and NSViewRepresentable, which enable the creation and updating of UIKit or AppKit views using imperative code. Conversely, SwiftUI views can be embedded into UIKit or AppKit view hierarchies using classes like UIHostingController and NSHostingViewController.

2. State-Driven Views:

   • SwiftUI views are state-driven, meaning they automatically update the UI when the underlying state changes. This reduces boilerplate code and minimizes update bugs. SwiftUI maintains a representation of the user interface behind the scenes, updating outputs as data changes.

3. Declarative Structure:

   • SwiftUI uses a declarative approach, where views are described as value types using structs. This allows for efficient data structures and performance optimization without compromising code organization.

4. Animations and Transitions:

   • SwiftUI provides powerful animation capabilities, allowing developers to set up animations on UIKit or AppKit views and drive them with SwiftUI, including custom animations. This is part of a broader effort to enhance UI animations and transitions across Apple's platforms.

5. Low-Level Control and Customization:

   • For developers looking to create unique custom experiences, SwiftUI offers APIs for low-level control, such as building custom control styles, using canvas for high-performance drawing, and applying custom Metal shaders directly to SwiftUI views.

For more detailed insights, you can refer to the Platforms State of the Union (35:12) and SwiftUI essentials (15:57) sessions.