Passing data from simple NSView to SwiftUI View - swift

Question

I'm making a macOS app with SwiftUI. I have a struct conforming to NSViewRepresentable, whose purpose is to detect the key code of whichever key was pressed. I want to pass the event.keyCode back to SwiftUI and save it into an environment object so I can use the key code elsewhere in my app.
I know I am supposed to use SwiftUI coordinators, but all tutorials and Stack Overflow questions I can find use ready-made classes such as UIPageControl or UISearchBar that have pre-configured delegates. I'm not sure what to do when using a simple custom NSView. Can somebody explain how to pass the data from the NSViewRepresentable struct into my #EnvironmentObject when using a custom NSView?
struct KeyboardEvent: NSViewRepresentable {
class KeyView: NSView {
override var acceptsFirstResponder: Bool { true }
override func keyDown(with event: NSEvent) {
print("\(event.keyCode)")
}
}
func makeNSView(context: Context) -> NSView {
let view = KeyView()
DispatchQueue.main.async {
view.window?.makeFirstResponder(view)
}
return view
}
func updateNSView(_ nsView: NSView, context: Context) {
}
}
struct ContentView: View {
#EnvironmentObject var input: KeyboardInput // save the keyCode here
var body: some View {
VStack {
Text(input.keyCode)
KeyboardEvent()
}
}
}
Right now it prints the key code normally to the Xcode console, so the detection works fine.

Answer 1

Here is a solution (with some replicated parts). Tested with Xcode 11.4 / macOS 10.15.4
class KeyboardInput: ObservableObject {
#Published var keyCode: UInt16 = 0
}
struct KeyboardEvent: NSViewRepresentable {
#Binding var keyStorage: UInt16 // << here !!
init(into storage: Binding<UInt16>) {
_keyStorage = storage
}
class KeyView: NSView {
var owner: KeyboardEvent? // << view holder
override var acceptsFirstResponder: Bool { true }
override func keyDown(with event: NSEvent) {
print("\(event.keyCode)")
owner?.keyStorage = event.keyCode
}
}
func makeNSView(context: Context) -> NSView {
let view = KeyView()
view.owner = self // << inject
DispatchQueue.main.async {
view.window?.makeFirstResponder(view)
}
return view
}
func updateNSView(_ nsView: NSView, context: Context) {
}
}
struct ContentView: View {
#EnvironmentObject var input: KeyboardInput // save the keyCode here
var body: some View {
VStack {
Text("Code: \(input.keyCode)")
KeyboardEvent(into: $input.keyCode) // << binding !!!
}
}
}