What is structural identity in SwiftUI?

Structural identity in SwiftUI refers to the concept that SwiftUI views are value types defined using structs instead of classes. This is because SwiftUI views are descriptions of what the current state of the UI should be, rather than long-lived object instances that receive imperative commands over time. SwiftUI takes these descriptions and creates an efficient data structure to represent them, maintaining this data structure behind the scenes to produce different outputs, such as what's shown on screen, gestures, interactive aspects of the view, and its accessibility representation.

This approach allows for breaking up one view into multiple views without hurting the performance of the app, enabling better code organization without compromising performance. Composition is a key part of SwiftUI, allowing for the creation of complex user interfaces by combining simpler views.

For more details, you can refer to the SwiftUI essentials session.