import SwiftUI

struct User: Identifiable {
    var id: Int

    init(id: Int) {
        self.id = id
    }
}

struct MyCell: View {
    let user: User
    private let randomHeight: Length

    init(user: User) {
        self.user = user
        randomHeight = Length.random(in: 4...6) * 10
//        randomHeight = 50
        print("MyCell initialized. id:", user.id)
    }

    var body: some View {
        print("MyCell builded. id:", user.id)
        return Text(String(user.id))
            .frame(height: randomHeight, alignment: .center)
    }
}

struct ContentView : View {
    var users: [User] = (0..<100).map(User.init(id:))
    @State var selected: Set<Int> = []

    var body: some View {
        List(users, selection: $selected, action: { user in
            if self.selected.contains(user.id) {
                print(user.id, "will remove")
                self.selected.remove(user.id)
                print(user.id, "did remove")
            } else {
                print(user.id, "will add")
                self.selected.insert(user.id)
                print(user.id, "did add")
            }
        }) { user in
            MyCell(user: user)
                .background(self.selected.contains(user.id) ? Color.red : Color.white)
        }
    }
}