import SwiftUI

struct FormAdvancedDemo: View {
  @State private var email = ""
  @State private var accepted = false
  var valid: Bool { email.contains("@") && accepted }
  var body: some View {
    Form {
      Section(header: Text("Account")) {
        TextField("Email", text: $email).keyboardType(.emailAddress)
        Toggle("Accept Terms", isOn: $accepted)
      }
      Section { Button("Submit") { } .disabled(!valid) }
    }
  }
}

                    

import SwiftUI

struct ContentView: View { var body: some View { FormAdvancedDemo() } }

                    

import SwiftUI

@main
struct MyApp: App { var body: some Scene { WindowGroup { ContentView() } } }