SwiftUI Environment Service

ContentView.swift

import SwiftUI

class SomeService: Observable {
  
  let message: String
  
  init(message: String) {
    self.message = message
  }
  
  func announce() {
    print(message)
  }
}

struct ContentView: View {
  
  @State var service = SomeService(message: "initialised")
  
    var body: some View {
      VStack {
        InnerView()
          .padding()
          .environment(service)
        HStack {
          Button("Use Service A") {
            service = SomeService(message: "using service a")
          }
          Button("Use Service B") {
            service = SomeService(message: "using service b")
          }
        }
        .buttonStyle(.borderedProminent)
      }
    }
}

struct InnerView: View {
  
  @Environment(SomeService.self) var service
  
  var body: some View {
    let _ = print("redrawing")
    VStack {
        Image(systemName: "globe")
            .imageScale(.large)
            .foregroundStyle(.tint)
        Text("Hello, world!")
      Button("Announce") {
        service.announce()
      }
    }
  }
}

#Preview {
    ContentView()
}