SwiftUI bug

As of Xcode 11.3.1 and 11.4-beta, there is a bug with updating a UIViewRepresentable. When a SwiftUI View passes an @ObservedObject to a UIViewRepresentable, and the UIViewRepresentable is a struct, SwiftUI fails to call the updateUIView method of the UIViewRepresentable when the observed object changes.

If the UIViewRepresentable is a final class, then its updateUIView is correctly called when the observable object changes.

Install and run

This should be ready to go: just clone this repo and run it in Xcode 11.3.1 or 11.4-beta.

Test structure

• A SwiftUI View with an @ObservedObject.
• The @ObservedObject changes every 1 second.
• The SwiftUI View's body contains two UIViewRepresentables:
  • one is a struct
  • the other one is a final class
• The SwiftUI View passes its @ObservedObject to the two UIViewRepresentables.

Expected behavior

• Both UIViewRepresentables update every 1 second.

Actual behavior

• The final class UIViewRepresentable updates correctly every 1 second.
• The struct UIViewRepresentable does NOT update.

Side note: the struct UIViewRepresentable does update when the device orientation is changed.