如何从 NSViewRepresentable / UIViewRepresentable 的协调器 class 中访问 EnvironmentObject？

Question

I got an EnvironmentObject named appState, which is accessed through some of my views to share data / states. The way I use them in a view is like this:

struct MetalView: NSViewRepresentable {
@EnvironmentObject var appState: AppState

How can I access appState from my view's Coordinator class?

When I try to call it in any way I've tried yet, I get this error:

"Instance member 'appState' of type 'MetalView' cannot be used on instance of nested type 'MetalView.Coordinator'"

Any clues?

Answer 1

Here is how I solved this:

AppState.swift:

class AppState: ObservableObject {
    
    static let shared = AppState()
    init () {} // TODO: was private init, find out if this has benefits
    
    @Published var currentView: String = "login"
    // add rest of shared stuff below

AppDelegate.swift:

func applicationDidFinishLaunching(_ aNotification: Notification) {
        let appState = AppState.shared

Access from SwiftUI Views:

struct ContentView: View {
    @EnvironmentObject var appState: AppState

Access from NSViewRepresentable / UIViewRepresentable Coordinator Class:

class Coordinator: NSObject, MTKViewDelegate {
...  
        func draw(in view: MTKView) {
            ...
            context.render((AppState.shared.rawImage ?? AppState.shared.rawImageOriginal)!,
                to: drawable.texture,
                commandBuffer: commandBuffer,
                bounds: AppState.shared.rawImageOriginal!.extent,
                colorSpace: colorSpace)
    }
...

This took me a lot of time to figure out, so I hope it can help some fellow beginning SwiftUI programmer...

If advanced programmers can improve on this, please do so I can learn from it.