SwiftUI is Apple’s declarative framework for building user interfaces. Instead of imperatively creating and mutating view objects the way UIKit does, a developer describes what the interface should look like for a given application state, and the framework keeps the rendered UI in sync as that state changes. Apple’s documentation presents SwiftUI as a way to build user interfaces “across all Apple platforms with the power of Swift” using a single, declarative set of tools and APIs.
Apple introduced SwiftUI at its Worldwide Developers Conference on June 3, 2019. In the company’s WWDC 2019 highlights, Apple framed SwiftUI as letting developers “build native apps across all Apple platforms” with far less code. Craig Federighi, Apple’s senior vice president of Software Engineering, said the new technologies made app development “faster, easier and more fun” and that SwiftUI “transforms user interface creation by automating large portions of the process and providing real-time previews.”
The framework is built on the Swift language and leans on its features, using result builders and a chainable modifier syntax so that layout, styling, and behavior read as a hierarchy of declarations. State management is a core concept: property wrappers such as the ones for local state and bindings let the framework track which pieces of data a view depends on and re-render only what changed when that data updates.
A signature part of the SwiftUI experience is the live preview integrated into Xcode. As code is edited, Xcode renders the resulting interface side by side in real time, and changes made in the visual canvas are reflected back in the source. This tightens the design-build-test loop compared with the older compile-and-run cycle.
SwiftUI did not replace UIKit so much as layer on top of and alongside it. Apple provided interoperability so SwiftUI views can host UIKit (and AppKit) views and vice versa, letting existing apps adopt SwiftUI incrementally. Across the releases that followed its 2019 debut, Apple expanded SwiftUI to cover more of each platform’s interface, positioning it as the forward-looking way to write Apple apps while UIKit remained fully supported.