How to add a TextField to Alert in SwiftUI?

Question

Anyone an idea how to create an Alert in SwiftUI that contains a TextField?

Answer 1

You can simply use UIAlertController directly. No need to roll your own alert dialog UI:

private func alert() {
    let alert = UIAlertController(title: "title", message: "message", preferredStyle: .alert)
    alert.addTextField() { textField in
        textField.placeholder = "Enter some text"
    }
    alert.addAction(UIAlertAction(title: "Cancel", style: .cancel) { _ in })
    showAlert(alert: alert)
}

func showAlert(alert: UIAlertController) {
    if let controller = topMostViewController() {
        controller.present(alert, animated: true)
    }
}

private func keyWindow() -> UIWindow? {
    return UIApplication.shared.connectedScenes
    .filter {$0.activationState == .foregroundActive}
    .compactMap {$0 as? UIWindowScene}
    .first?.windows.filter {$0.isKeyWindow}.first
}

private func topMostViewController() -> UIViewController? {
    guard let rootController = keyWindow()?.rootViewController else {
        return nil
    }
    return topMostViewController(for: rootController)
}

private func topMostViewController(for controller: UIViewController) -> UIViewController {
    if let presentedController = controller.presentedViewController {
        return topMostViewController(for: presentedController)
    } else if let navigationController = controller as? UINavigationController {
        guard let topController = navigationController.topViewController else {
            return navigationController
        }
        return topMostViewController(for: topController)
    } else if let tabController = controller as? UITabBarController {
        guard let topController = tabController.selectedViewController else {
            return tabController
        }
        return topMostViewController(for: topController)
    }
    return controller
}

Most of this code is just boilerplate to find the ViewController that should present the alert. Call alert() e.g. from the action of a button:

struct TestView: View {
    var body: some View {
        Button(action: { alert() }) { Text("click me") }
     }
}

Please beware though that there seems to be a bug in beta 5 and onward that can sometimes cause the emulator to freeze once a text field is shown: Xcode 11 beta 5: UI freezes when adding textFields into UIAlertController