SwiftUI @Binding update doesn't refresh view

Question

I feel like I\'m missing something very basic, but this example SwiftUI code will not modify the view (despite the Binding updating) when the button is clicked

Tutorials

Answer 1

SwiftUI View affects @Binding. @State affects SwiftUI View. @State var affects the view, but to affect another @State it must be used as binding by adding leading $ to value name and it works only inside SwiftUI.

To trigger SwiftUI change from outside, i.e. to deliver/update Image, use Publisher that looks like this:

// Declare publisher in Swift (outside SwiftUI)    
public let imagePublisher = PassthroughSubject()

// And within SwiftUI it must be handled:
struct ContentView: View {
// declare @State that updates View:
    @State var image: Image = Image(systemName: "photo")
    var body: some View {
// Use @State image declaration
                image
// Subscribe this value to publisher "imagePublisher"
                    .onReceive(imagePublisher, perform: { (output: Image) in
// Whenever publisher sends new value, old one to be replaced
                        self.image = output
                    })
    }
}

// And this is how to send value to update SwiftUI from Swift:
imagePublisher.send(Image(systemName: "photo"))