SwiftUI vs UIKit: what is the difference?
SwiftUI and UIKit are both Apple frameworks for building user interfaces on iOS, but they take different approaches. UIKit is the older, imperative framework that has powered iOS apps since 2008. SwiftUI is the newer, declarative framework introduced in 2019 and is Apple's recommended default for new development. The core difference is how you describe the interface.
How they differ
UIKit is imperative. You create UI elements and then write step-by-step instructions to change them: add a row here, hide a button there, update this label when data changes. This gives precise control over every detail and every transition, at the cost of more code and more places for the screen and the data to drift out of sync.
SwiftUI is declarative. You describe what the interface should look like for the current state, and the framework updates the screen when the state changes. This typically means far less code and removes a whole class of bugs caused by manual UI updates. The tradeoff is that, as the newer framework, SwiftUI occasionally lacks a fine-grained capability that UIKit exposes, though that gap narrows with each release.
When to use each
For most new apps, SwiftUI is the sensible default. It is faster to write, easier to keep correct, and the direction Apple is steering the platform, with live previews that speed up UI work. UIKit still makes sense when you need very specific control that SwiftUI does not yet offer, or when you are working in an existing UIKit codebase where matching the surrounding code is simpler than mixing frameworks.
A key point is that the two are not mutually exclusive. Apple provides bridges so UIKit views can live inside SwiftUI and the reverse, which is common when migrating an older app gradually or filling a one-off gap.
Which AppFlight uses
AppFlight generates native SwiftUI, the modern declarative framework, when building iOS apps from a prompt, and runs the result in a live iOS simulator. SwiftUI's concise, state-driven style maps cleanly from a plain-English description to working screens, and the output is real, readable Swift you can edit.
FAQ
Should I use SwiftUI or UIKit for a new app?
For most new apps, SwiftUI is the recommended default. It needs less code and is where Apple is investing. UIKit may still be chosen for very fine-grained control or to match an existing UIKit codebase.
Can SwiftUI and UIKit be used together?
Yes. Apple provides ways to embed UIKit views inside SwiftUI and SwiftUI views inside UIKit, so an app can mix both. This is common when migrating an older app or filling a gap in one framework.
Is UIKit being deprecated?
No. UIKit is still fully supported and widely used. SwiftUI is the newer default, but UIKit remains available and is sometimes the better fit for specific needs.