A long time ago we placed ReactiveX — a family of open-source frameworks for reactive programming — into the Adopt ring of the Radar. In 2017, we mentioned the addition of RxSwift, which brought reactive programming to iOS development using Swift. Since then, Apple has introduced its own take on reactive programming in the form of the Combine framework. Combine has become our default choice for apps that support iOS 13 as an acceptable deployment target. It's easier to learn than RxSwift and integrates really well with SwiftUI. If you're planning to convert an existing application from RxSwift to Combine or work with both in the same project, you might want to look at RxCombine.