Show alert in Swift – Simplify using protocol

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Alert as UIAlertController is used in almost every iOS application. It is one of the most basic components of the application. We can simplify the UIAlertController using protocol. In this short article, I have created AlertDisplaying protocol to resolve alert related code duplication.

Alert can contain a title, a message, style(alert or action sheet), one or multiple actions(alert buttons) and an alert text field.

Alert protocol – AlertDisplaying

typealias AlertAction = (UIAlertAction) -> Void
protocol AlertDisplaying {
    func displayAlert(title: String, message: String)
    func displayFailureAlert(message: String?)
    func displayAlertWithAction(title: String?, message: String?, action: AlertAction?)
}

Now add the default implementation of AlertDisplaying protocol

extension AlertDisplaying where Self: UIViewController {

    func displayAlert(title: String, message: String) {
        displayAlert(title: title,
                     message: message,
                     actions: [UIAlertAction(title: "Ok", style: .cancel, handler: nil)])

    }

    func displayFailureAlert(message: String? = "") {
        displayAlert(title: "Error",
                     message: message?.isEmpty == true ? "Something went wrong!" : message,
                     actions: [UIAlertAction(title: "Cancel", style: .destructive, handler: nil)])
    }

    func displayAlertWithAction(title: String?, message: String?, action: AlertAction?) {
        displayAlert(title: title,
                     message: message,
                     actions: [UIAlertAction(title: "Yes", style: .default, handler: action),
                               UIAlertAction(title: "No", style: .cancel, handler: nil)])
    }

    private func displayAlert(title: String? = "", message: String? = "", actions: [UIAlertAction] = []) {
        let alertController = UIAlertController(title: title, message: message, preferredStyle: .alert)
        actions.forEach { (action) in
            alertController.addAction(action)
        }
        present(alertController, animated: true, completion: nil)
    }
}

We can simply use it by conforming the AlertDisplaying protocol

class ViewController: UIViewController, AlertDisplaying {

    @IBAction func displayAlert(sender: UIButton) {
        displayFailureAlert()

        // Or

        displayAlert(title: "Success", message: "Product submitted")

        // Or

        displayAlertWithAction(title: "Product delete",
                               message: "Do you want to delete this product?") { _ in
            // ...
        }
    }
}

Written by

ISHTIAK AHMED

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