swiftui state variable count lost what it stored

Question

when I click onTapGesture event to setup

  self.showDetailView = true
  self.count = 5

the sheet will popup, but the self.count always be 0, not be 5. so the code Text("5555") will never be hitt.

it seems state variable count lost what it stored.

import SwiftUI

struct ContentView: View {
    @State var showDetailView = false
    @State var count = 0
    var testArr = [1,2,3,4,5]
    var body: some View {
        
        NavigationView {
            List(testArr.indices){ indice in
                Text("row num (indice)")
                    .onTapGesture{
                        
                        self.showDetailView = true
                        self.count = 5
                        }
                
                }
                .sheet(isPresented: self.$showDetailView) {
                    if self.count == 0{
                        //  print("count = 0")
                    }
                    if  self.count == 5{
                        Text("5555")
                    }
                
                }
            
                .navigationBarTitle("Your Reading")
        }
        }
    }

    struct ContentView_Previews: PreviewProvider {
        static var previews: some View {
            ContentView()
        }
    }

Answer 1

You can use @Binding to pass value to child view:

struct DetailView: View {
    @Binding var count: Int

    var body: some View {
        if count == 5 {
            Text("5555")
        } else {
            EmptyView()
        }

    }
}

in your .sheet:

.sheet(isPresented: self.$showDetailView) {
    if self.count == 0 {
        //  print("count = 0")
    }
    DetailView(count: $count)

}