iosuikitswiftuiuialertcontrolleruialertaction

SwiftUI: UIAlertController's textField does not responding in UIAlertAction


I need to use UIAlertContoller, as SwiftUI's Alert does not support TextField.

I must not use Custom created AlertView, due to various reason(Accessibility, DynamicType, Dark Mode support etc).

Basic Idea is, SwiftUI's alert must hold TextField & entered text must be reflect back for usage.

I created a SwiftUI view by Conforming to UIViewControllerRepresentable following is working code.

struct AlertControl: UIViewControllerRepresentable {

    typealias UIViewControllerType = UIAlertController

    @Binding var textString: String
    @Binding var show: Bool

    var title: String
    var message: String

    func makeUIViewController(context: UIViewControllerRepresentableContext<AlertControl>) -> UIAlertController {

        let alert = UIAlertController(title: title, message: message, preferredStyle: .alert)

        alert.addTextField { textField in
            textField.placeholder = "Enter some text"
        }

        let cancelAction = UIAlertAction(title: "cancel", style: .destructive) { (action) in
            self.show = false
        }

        let submitAction = UIAlertAction(title: "Submit", style: .default) { (action) in
            self.show = false
        }

        alert.addAction(cancelAction)
        alert.addAction(submitAction)

        return alert
    }

    func updateUIViewController(_ uiViewController: UIAlertController, context: UIViewControllerRepresentableContext<AlertControl>) {

    }

    func makeCoordinator() -> AlertControl.Coordinator {
        Coordinator(self)
    }

    class Coordinator: NSObject, UITextFieldDelegate {

        var control: AlertControl

        init(_ control: AlertControl) {
            self.control = control
        }

        func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {
            if let text = textField.text {
                self.control.textString = text
            }

            return true
        }
    }
}

// SwiftUI View in some content view
 AlertControl(textString: self.$text,
                             show: self.$showAlert,
                             title: "Title goes here",
                             message: "Message goes here")

Problem:

There is No activity in Alert Action when it is tapped. I put breakpoints to check, but it never hit there.

Even UITextFieldDelegate's function never hit.

func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool

Edit: cancelAction or submitAction does not triggers on tap of these fields.


Solution

  • Here is full demo module for solution that works. Tested with Xcode 11.4 / iOS 13.4

    demo

    See also important comments inline

    struct AlertControl: UIViewControllerRepresentable {
    
        @Binding var textString: String
        @Binding var show: Bool
    
        var title: String
        var message: String
    
        func makeUIViewController(context: UIViewControllerRepresentableContext<AlertControl>) -> UIViewController {
            return UIViewController() // holder controller - required to present alert
        }
    
        func updateUIViewController(_ viewController: UIViewController, context: UIViewControllerRepresentableContext<AlertControl>) {
            guard context.coordinator.alert == nil else { return }
            if self.show {
                let alert = UIAlertController(title: title, message: message, preferredStyle: .alert)
                context.coordinator.alert = alert
    
                alert.addTextField { textField in
                    textField.placeholder = "Enter some text"
                    textField.text = self.textString            // << initial value if any
                    textField.delegate = context.coordinator    // << use coordinator as delegate
                }
                alert.addAction(UIAlertAction(title: "cancel", style: .destructive) { _ in
                    // your action here
                })
                alert.addAction(UIAlertAction(title: "Submit", style: .default) { _ in
                    // your action here
                })
    
                DispatchQueue.main.async { // must be async !!
                    viewController.present(alert, animated: true, completion: {
                        self.show = false  // hide holder after alert dismiss
                        context.coordinator.alert = nil
                    })
                }
            }
        }
    
        func makeCoordinator() -> AlertControl.Coordinator {
            Coordinator(self)
        }
    
        class Coordinator: NSObject, UITextFieldDelegate {
            var alert: UIAlertController?
            var control: AlertControl
            init(_ control: AlertControl) {
                self.control = control
            }
    
            func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {
                if let text = textField.text as NSString? {
                    self.control.textString = text.replacingCharacters(in: range, with: string)
                } else {
                    self.control.textString = ""
                }
                return true
            }
        }
    }
    
    // Demo view for Alert Controll
    struct DemoAlertControl: View {
        @State private var text = ""
        @State private var showAlert = false
    
        var body: some View {
            VStack {
                Button("Alert") { self.showAlert = true }
                    .background(AlertControl(textString: self.$text, show: self.$showAlert,
                             title: "Title goes here", message: "Message goes here"))
                Text(self.text)
            }
        }
    }