Photo by Hannah Busing on UnsplashOne of the biggest announcements at WWDC 2019 was SwiftUI — its declarative approach makes building UIs a breeze, and it’s easy to see why people are so excited about it. The hidden gem, however, was the Combine framework, which didn’t get as much fanfare as I think it deserves. Apple have put their sign of approval on Functional Reactive Programming, and soon it