Customizable NSAlert with suppression checkbox in SwiftUI

SwiftUI_NSAlertExampleApp.swift

//
//  SwiftUI_NSAlertExampleApp.swift
//  SwiftUI_NSAlertExample
//
//  Created by Stephan Casas on 6/20/23.
//
//  This example requires the [NSViewProxy](https://github.com/stephancasas/NSViewProxy)
//  package to acquire the pre-draw window context in `ContentView`.
//

import SwiftUI
import Combine;
import NSViewProxy;

// MARK: - Main App

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

// MARK: - Content View

struct ContentView: View {
    
    @State private var alertResult: String? = nil;
    private var alertSubscriber = PassthroughSubject<String, Never>();
    
    var body: some View {
        VStack(content: {
            Button(action: self.showAlert, label: {
                Text("Show Alert")
            })
            
            if let alertResult = self.alertResult {
                Text(alertResult).padding()
            }
        })
        .padding()
        .proxy(to: .window, using: self.configureCustomAlert)
        .onReceive(self.alertSubscriber, perform: self.handleAlertResult)
    }
    
    // MARK: - Handle Custom Alert Result
    
    private func handleAlertResult(_ result: String) {
        self.alertResult = result;
    }
    
    // MARK: - Configure Custom Alert
    
    @State private var showAlert: () -> Void = { }
    
    private func configureCustomAlert(_ window: NSWindow) {
        self.showAlert = {
            let customAlert = NSAlert();
            customAlert.alertStyle = .critical;
            customAlert.messageText = "Are you sure you want to continue?";
            customAlert.informativeText = "What you're doing sounds like a terrible idea.";
            
            /// The value of `NSApplication.ModalResponse` in the provided callback
            /// is `RawRepresentable<Int>` with values starting at 1000.
            ///
            let options: [Int: String] = [1000: "Continue", 1001: "Cancel"];
            
            customAlert.addButton(withTitle: options[1000]!)
                .hasDestructiveAction = true;
            customAlert.addButton(withTitle: options[1001]!);
            
            customAlert.showsSuppressionButton = true;
            customAlert.suppressionButton?.title = "Don't tell me what to do";
            
            customAlert.beginSheetModal(
                for: window,
                completionHandler: { (response: NSApplication.ModalResponse) in
                    let choice = options[response.rawValue] ?? "Unknown";
                    let suppression = (customAlert.suppressionButton?.state.rawValue ?? 0) == 1;
                    self.alertSubscriber.send(
                        "User picked \"\(choice)\(suppression ? "\" and will ignore future alerts." : ".\"")"
                    );
                });
        };
    }
}