How to update a SwiftUI view state from outside (UIViewController for example)

Question

I have a SwiftUI view:

struct CatView : View {

    @State var eyesOpened: Bool = false

    var body: some View {         


        

Answer 1

There is something called the notification center that you could use. In short, it is a way that views can communicate between each other without actually modifying anything in each other.

How it works is view A sends a notification to a central hub from which view B hears said notification. When view B hears the notification it activates, and calls a function defined by the user.

For a more detailed explanation, you can refer to: https://learnappmaking.com/notification-center-how-to-swift/

Answer 2

@State is the wrong thing to use here. You'll need to use @ObservedObject.

@State: Used for when changes occur locally to your SwiftUI view - ie you change eyesOpened from a toggle or a button etc from within the SwiftUI view it self.

@ObservedObject: Binds your SwiftUI view to an external data source - ie an incoming notification or a change in your database, something external to your SwiftUI view.

I would highly recommend you watch the following WWDC video - Data Flow Through SwiftUI