SwiftUI @State emulation with SwiftUI memory

SwiftUI-SimpleState.swift

// UM EECS 441

import SwiftUI

@propertyWrapper
struct SimpleState<T>: DynamicProperty {
    private var _state: State<T>    // references SwiftUI memory outside of struct
    var wrappedValue: T {
        get { _state.wrappedValue }  // accesses reference to SwiftUI memory
        nonmutating set { _state.wrappedValue = newValue }    // no change to reference
    }
    var projectedValue: Binding<T> {
        Binding(
            get: { wrappedValue },
            set: { wrappedValue = $0 }
        )
    }
    init(wrappedValue: T) {
        _state = State(wrappedValue: wrappedValue)   // allocate space in SwiftUI memory
    }                                               // also comes with subscription!
}

struct ChildView: View {
    @Binding var count: Int
    var body: some View {
        Button("+1") { count += 1 }
    }
}

struct ContentView: View {
    @SimpleState var count = 0
    var body: some View {
        VStack {
            Text("\(count)").font(.system(size: 28))
            ChildView(count: $count)
        }
        .font(.system(size: 28))        
    }
}