Example for demonstrating the delay on setting the bound variable to nil, when sheet is dismissed by drag

sheet-delay.swift

import SwiftUI

struct ContentView: View {
    private enum ActiveSheet: Identifiable {
        case first, second
        var id: Int { hashValue }
    }

    @State private var activeSheet: ActiveSheet?

    var body: some View {
        VStack(spacing: 30) {
            if activeSheet == nil {
                Button("First sheet") { activeSheet = .first }
                Button("Second sheet") { activeSheet = .second }
            } else {
                Text("Sheet still open...")
            }
        }
        .frame(maxWidth: .infinity, maxHeight: .infinity)
        .sheet(item: $activeSheet, onDismiss: dismiss) { sheet in
            switch sheet {
            case .first:
                VStack(spacing: 30) {
                    Text("First sheet")
                    Button("Close", action: dismiss)
                }
                .frame(maxWidth: .infinity, maxHeight: .infinity)
                .background(Color.blue.opacity(0.3))

            case .second:
                VStack(spacing: 30) {
                    Text("Second sheet")
                    Button("Close", action: dismiss)
                }
                .frame(maxWidth: .infinity, maxHeight: .infinity)
                .background(Color.green.opacity(0.3))
            }
        }
    }

    func dismiss() {
        activeSheet = nil
    }
}

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