Reinstantiate an #EnvironmentObject in a view - swift

Question

In my application, I have the need to reinstantiate an #EnvironmentObject at the tap of a button. Where is the right spot to do that?
Here's a screenshot of my view - in the Archived Objects list, I want to have immutable objects. So, when I tap Archive Object, I want to add the current object to the array and create a new current object.
A simplified version of the app looks as follows.
I instantiate the object in the SceneDelegate:
class SceneDelegate: UIResponder, UIWindowSceneDelegate {
var window: UIWindow?
var myObject = MyObject()
let myObjects = MyObjects()
func scene(_ scene: UIScene, willConnectTo session: UISceneSession, options connectionOptions: UIScene.ConnectionOptions) {
let contentView = ContentView()
.environmentObject(myObject)
.environmentObject(myObjects)
if let windowScene = scene as? UIWindowScene {
let window = UIWindow(windowScene: windowScene)
window.rootViewController = UIHostingController(rootView: contentView)
self.window = window
window.makeKeyAndVisible()
}
}
//.....
}
Here's my models:
class MyObject: ObservableObject, Identifiable {
#Published var id = UUID()
}
class MyObjects: ObservableObject {
#Published var values: [MyObject] = [
MyObject(),
MyObject()
]
}
In my view, I have the need to put my current object to an (archive) array and then create a new current object to work with. Here's what I'm trying:
struct ContentView: View {
#EnvironmentObject var currentObject: MyObject
#EnvironmentObject var objects: MyObjects
var sceneDelegate: UISceneDelegate {
guard let windowScene = UIApplication.shared.connectedScenes.first as? UIWindowScene,
let sd = windowScene.delegate as? SceneDelegate else { fatalError() }
return sd
}
var body: some View {
VStack {
Form {
Section(header: Text("Current Object")) {
Text(currentObject.id.uuidString)
}
Section(header: Text("Archived Objects")) {
List(objects.values, id: \.id) { object in
Text(object.id.uuidString)
}
Button(action: {
self.objects.values.append(self.currentObject)
// as the environment object is get only, I cannot reinstantiate it here...
// self.currentObject = MyObject()
}) {
Text("Archive Object")
}
}
}
Spacer()
}
}
}

Answer 1

Here is a solution. See comments inline.
Tested with Xcode 11.4 / iOS 13.4
struct ContentView_Previews: PreviewProvider {
static var previews: some View {
// Usage
ContentView(current: MyObject())
.environmentObject(MyObjects())
}
}
struct ContentView: View {
#EnvironmentObject var objects: MyObjects
#State private var current: MyObject // tracks current
init(current: MyObject) {
_current = State(initialValue: current)
}
var body: some View {
// rebuilt on *current* changed
ContentInnerView(current: $current)
.environmentObject(current)
}
struct ContentInnerView: View {
#Binding var current: MyObject // change current
#EnvironmentObject var objects: MyObjects
#EnvironmentObject var currentObject: MyObject
init(current: Binding<MyObject>) {
_current = current
}
var sceneDelegate: UISceneDelegate {
guard let windowScene = UIApplication.shared.connectedScenes.first as? UIWindowScene,
let sd = windowScene.delegate as? SceneDelegate else { fatalError() }
return sd
}
var body: some View {
VStack {
Form {
Section(header: Text("Current Object")) {
Text(currentObject.id.uuidString)
}
Section(header: Text("Archived Objects")) {
List(objects.values, id: \.id) { object in
Text(object.id.uuidString)
}
Button(action: {
self.objects.values.append(self.currentObject)
self.current = MyObject() // << works !!
}) {
Text("Archive Object")
}
}
}
Spacer()
}
}
}
}