TextAlert

TextAlert.swift

//
//  ContentView.swift
//
//  Created by Chris Eidhof on 20.04.20.
//  Copyright © 2020 objc.io. All rights reserved.
//

import SwiftUI
import UIKit

extension UIAlertController {
    convenience init(alert: TextAlert) {
        self.init(title: alert.title, message: nil, preferredStyle: .alert)
        addTextField { $0.placeholder = alert.placeholder }
        addAction(UIAlertAction(title: alert.cancel, style: .cancel) { _ in
            alert.action(nil)
        })
        let textField = self.textFields?.first
        addAction(UIAlertAction(title: alert.accept, style: .default) { _ in
            alert.action(textField?.text)
        })
    }
}



struct AlertWrapper<Content: View>: UIViewControllerRepresentable {
    @Binding var isPresented: Bool
    let alert: TextAlert
    let content: Content
    
    func makeUIViewController(context: UIViewControllerRepresentableContext<AlertWrapper>) -> UIHostingController<Content> {
        UIHostingController(rootView: content)
    }
    
    final class Coordinator {
        var alertController: UIAlertController?
        init(_ controller: UIAlertController? = nil) {
            self.alertController = controller
        }
    }
    
    func makeCoordinator() -> Coordinator {
        return Coordinator()
    }
    
    
    func updateUIViewController(_ uiViewController: UIHostingController<Content>, context: UIViewControllerRepresentableContext<AlertWrapper>) {
        uiViewController.rootView = content
        if isPresented && uiViewController.presentedViewController == nil {
            var alert = self.alert
            alert.action = {
                self.isPresented = false
                self.alert.action($0)
            }
            context.coordinator.alertController = UIAlertController(alert: alert)
            uiViewController.present(context.coordinator.alertController!, animated: true)
        }
        if !isPresented && uiViewController.presentedViewController == context.coordinator.alertController {
            uiViewController.dismiss(animated: true)
        }
    }
}

public struct TextAlert {
    public var title: String
    public var placeholder: String = ""
    public var accept: String = "OK"
    public var cancel: String = "Cancel"
    public var action: (String?) -> ()
}

extension View {
    public func alert(isPresented: Binding<Bool>, _ alert: TextAlert) -> some View {
        AlertWrapper(isPresented: isPresented, alert: alert, content: self)
    }
}

struct ContentView: View {
    @State var showsAlert = false
    var body: some View {
        VStack {
            Text("Hello, World!")
            Button("alert") {
                self.showsAlert = true
            }
        }
        .alert(isPresented: $showsAlert, TextAlert(title: "Title", action: {
            print("Callback \($0 ?? "<cancel>")")
        }))
    }
}

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

When I try it on iOS 15, it does not work well with the automatic keyboard avoidance introduced in iOS 14. The SwiftUI views below the alert move around when the keyboard for the alert's text field appears.

Other than wrapping everything in a ScrollView, the only workaround I've seen so far is setting .ignoresSafeArea(.keyboard) in combination with this:
https://steipete.com/posts/disabling-keyboard-avoidance-in-swiftui-uihostingcontroller/