How SwiftUI works under the hood?

SwiftUI operates under the hood by using a declarative approach to define user interfaces. Here are some key points about how it works:

1. Declarative Views: SwiftUI views are descriptions of what the current state of the UI should be. They are not long-lived object instances that receive imperative commands over time. Instead, they are value types defined using structs. SwiftUI takes these descriptions and creates an efficient data structure to represent them, which is used to produce different outputs like what's shown on screen, gestures, and accessibility features.

2. State-Driven Updates: SwiftUI is state-driven, meaning that when your view state changes, SwiftUI automatically updates the UI. This eliminates boilerplate code and reduces update bugs. SwiftUI maintains a representation of the user interface behind the scenes, and as data changes, new view values are created and used to update the UI.

3. Interoperability: SwiftUI offers seamless interoperability with UIKit and AppKit. You can use views or view controllers from these frameworks within SwiftUI using protocols like UIViewRepresentable. Conversely, you can embed SwiftUI views into UIKit or AppKit view hierarchies using classes like UIHostingController.

4. Animations and Transitions: SwiftUI builds on data-driven updates to provide animations. You can wrap state changes with animations, and SwiftUI applies default or custom transitions to the views.

5. Platform-Specific APIs: While SwiftUI provides a common set of components across platforms, it also offers specialized APIs for each platform, allowing you to tailor your app's UI to the unique characteristics of each device.

For more detailed insights, you can refer to the SwiftUI essentials session from WWDC 2024.