Alert Service

AlertService.swift

import UIKit

typealias VoidClosure = () -> Void

typealias AlertAction = (title: String, action: VoidClosure?, style: UIAlertActionStyle)

final class AlertService {

    static let shared = AlertService()

    fileprivate(set) lazy var alertControllerStyle: UIAlertControllerStyle = .alert

    let errorTitle: String
    let okTitle: String
    let cancelTitle: String

    init(errorTitle: String = "Error",
         okTitle: String = "OK",
         cancel: String = "Cancel") {
        self.errorTitle = errorTitle
        self.okTitle = okTitle
        cancelTitle = cancel
    }

    func showMessage(_ message: String, title: String? = nil, onDismiss: (() -> Void)? = nil) {
        showMessage(message, title: title, actions: nil, onDismiss: onDismiss)
    }

    func showErrorMessage(_ message: String, onDismiss: (() -> Void)? = nil) {
        showMessage(message, title: errorTitle, actions: nil, onDismiss: onDismiss)
    }

    func showMessage(_ message: String?,
                     title: String?,
                     actions: [AlertAction]?,
                     preferredStyle: UIAlertControllerStyle = .actionSheet,
                     presenter: UIViewController? = UIApplication.topViewController,
                     onDismiss: (() -> Void)? = nil) {
        let alertController = alertControllerWith(message, title: title, actions: actions, preferredStyle: preferredStyle, onDismiss: onDismiss)
        if let _presenter = presenter {
            _presenter.present(alertController, animated: true, completion: nil)
        }
    }
}

// MARK: - Private
private extension AlertService {

    func alertControllerWith(_ message: String?, title: String?, actions: [AlertAction]?,
                             preferredStyle: UIAlertControllerStyle = .actionSheet, onDismiss: (() -> Void)? = nil) -> UIAlertController {
        let alert = UIAlertController(title: title, message: message, preferredStyle: preferredStyle)
        alert.loadViewIfNeeded()
        if let actArray = actions { // map actions
            actArray.forEach { title, alertAction, style in
                let action = UIAlertAction(title: title, style: UIAlertActionStyle(rawValue: style.rawValue) ?? .default, handler: { (_) -> Void in
                    alertAction?()
                    alert.dismiss(animated: true, completion: onDismiss)
                })
                alert.addAction(action)
            }
        } else { // add ok button if there is no actions
            let okAction = UIAlertAction(title: okTitle, style: .default) { (_) -> Void in
                alert.dismiss(animated: true, completion: onDismiss)
            }
            alert.addAction(okAction)
        }
        return alert
    }
}

// MARK: - Top view controller
extension UIApplication {
    
    static var topViewController: UIViewController? {
        return UIApplication.shared.topViewController
    }
    
    var topViewController: UIViewController? {
        guard let rootController = keyWindow?.rootViewController else {
            return nil
        }
        return UIViewController.topViewController(rootController)
    }
}

// MARK: - Top view controller
extension UIViewController {
    
    static func topViewController(_ viewController: UIViewController) -> UIViewController {
        guard let presentedViewController = viewController.presentedViewController else {
            return viewController
        }
        if let navigationController = presentedViewController as? UINavigationController {
            if let visibleViewController = navigationController.visibleViewController {
                return topViewController(visibleViewController)
            }
        } else if let tabBarController = presentedViewController as? UITabBarController {
            if let selectedViewController = tabBarController.selectedViewController {
                return topViewController(selectedViewController)
            }
        }
        return topViewController(presentedViewController)
    }
}