How to get @Environment or @EnvironmentObject inside ObservableObject

Saw this interesting question on Stackoverflow and thought I would answer it. The trick is to use `DynamicProperty as an intermediary as follows:

class MyObject: ObservableObject {
    var context: NSManagedObjectContext? {
        didSet {
            if oldValue != context {
                // do something
            }
        }
    }
}

struct MyProperty: DynamicProperty {
    @Environment(\.managedObjectContext) private var viewContext
    @StateObject var object = MyObject()

    func update() {
        // environment vars now are valid
        object.context = viewContext    
    }
}

struct MyView {
    var myProperty = MyProperty()

    // update is called on myProperty before this
    var body: some View {
    }
}