EnvironmentObjectとBinding

SwiftUIEnvironmentObject.swift

//: A UIKit based Playground for presenting user interface

import UIKit
import PlaygroundSupport
import SwiftUI

struct ContentView: View {

    @EnvironmentObject var countSetting: CountSetting
    
    var body: some View {
        NavigationView {
            List {
                NavigationLink.init(destination: AnotherView()) {
                    ChildView(value: .init(get: { self.countSetting.count }, set: { _ in }))
                }
            }
        }
    }
}

struct ChildView: View {
    
    @Binding var value: Int
    
    var body: some View {
        HStack {
            Text("回数")
            Spacer()
            Text("\(value)")
        }
        .navigationBarTitle("親View", displayMode: .inline)
    }
    
}

struct AnotherView: View {
    
    @EnvironmentObject var countSetting: CountSetting
    
    var body: some View {
        VStack {
            Spacer()
            Text("回数を")
            Button.init("増やす") {
                self.countSetting.count += 1 //１増やす
            }.padding()
            Spacer()
        }.navigationBarTitle("もう一つのView", displayMode: .inline)
    }
    
}

/// classにする
class CountSetting: ObservableObject {
    @Published var count: Int = 0
}

// Present the view controller in the Live View window
let contentView = ContentView()
    .environmentObject(CountSetting())

PlaygroundPage.current.liveView = UIHostingController(rootView: contentView)