MyBagView

import SwiftUI

class MBData: ObservableObject{
    @Published var MBkosu : Int{
        didSet{
            UserDefaults.standard.set(MBkosu,forKey:"MBkey")
        }
    }
    init(){
        MBkosu = UserDefaults.standard.object(forKey:"MBkey") as? Int ?? 0
    }
}

struct MyBagView: View{
    @EnvironmentObject var mbData : MBData
    @State var MBkosu:Int = 0
    let MBpar = 47
    let MBtanka = 3
        var body : some View{
            VStack(alignment: . leading, spacing: 20){
                Image("マイバッグ")
                    .resizable()
                    .resizable().aspectRatio(contentMode: .fill)
                    .frame(width:300,height:300)
                    .clipped()
                    .cornerRadius(10)
                    .shadow(radius:10)
                    .foregroundColor(.black)
                Text ("\(MBpar)gのCO2削減     \(MBtanka)円の節約")
                    
                Stepper(value: $mbData.MBkosu, in: 0...100000, step:1) {
                    Text("行動回数:\(mbData.MBkosu)")
                }.frame(width:240)
                    
                let MBsoukei = MBpar * mbData.MBkosu
                let MBsougaku = mbData.MBkosu * MBtanka
                Text("総削減量:\(MBsoukei)g").font(.headline)
                + Text("(概算)").font(.footnote)
                Text("節約できたお金:\(MBsougaku)円")
            }
        }
    }

struct MyBagView_Previews: PreviewProvider {
    static var previews: some View {
        MyBagView()
            .environmentObject(MBData())
    }
}