How does swiftui work?

SwiftUI is a framework introduced by Apple for building user interfaces across all Apple platforms using a declarative Swift syntax. Here are some key points about how SwiftUI works:

1. Declarative Syntax: SwiftUI uses a declarative approach to define user interfaces. Instead of specifying the steps to create and update the UI, you describe what the UI should look like and how it should behave. SwiftUI takes care of the rest. For example, you can create a horizontal stack with a label, spacer, and text using simple, declarative code.

2. Views as Value Types: SwiftUI views are value types defined using structs, not classes. This means they are lightweight and can be easily created and destroyed. Views in SwiftUI are descriptions of the UI's current state, not long-lived object instances that receive imperative commands over time.

3. State-Driven: SwiftUI automatically updates the UI when the state changes. This eliminates the need for boilerplate code and reduces the likelihood of update bugs. When data changes, new view values are created and given to SwiftUI, which then updates the UI accordingly.

4. Composition: SwiftUI encourages breaking down the UI into small, reusable components. This compositional approach allows you to organize your code in a way that is both maintainable and performant.

5. Adaptivity: SwiftUI views are adaptive and can automatically adjust to different environments, such as dark mode, dynamic type, and localization. Xcode previews allow you to see how your views will look in different contexts without needing to run the app repeatedly.

6. Interoperability: SwiftUI can interoperate with other frameworks like UIKit and AppKit. This means you can use SwiftUI alongside existing codebases and take advantage of the rich capabilities of these frameworks.

7. Cross-Platform: SwiftUI is designed to work across all Apple platforms, including iOS, macOS, watchOS, and tvOS. It provides a common set of high and low-level components, with specialized APIs for each platform to handle unique design considerations.

For a more detailed understanding, you can refer to the SwiftUI essentials session from WWDC 2024, which covers the fundamentals of views, built-in capabilities, and interoperability across platforms.