Extension to provide simpler support for showing UIAlertController is "common" scenarios

UIViewController+Alert.swift

import Foundation
import UIKit

extension UIViewController {

	@objc func presentErrorAlertWith(message: String,
															preferredStyle: UIAlertController.Style = .alert,
															handler: AlertActionHandler? = nil) {
		guard Thread.isMainThread else {
			DispatchQueue.main.async(execute: {
				self.presentErrorAlertWith(
					message: message)
			})
			return
		}
		
		presentOkAlertWith(title: "Error", message: message, preferredStyle: preferredStyle, handler: handler)
	}

	@objc func presentAlertWith(title: String? = nil,
													 message: String,
													 preferredStyle: UIAlertController.Style = .alert,
													 actions: [UIAlertAction]) {
		guard Thread.isMainThread else {
			DispatchQueue.main.async(execute: {
				self.presentAlertWith(
					title: title,
					message: message,
					actions: actions)
			})
			return
		}
		let alertController = UIAlertController(title: title,
																						message: message,
																						preferredStyle: .alert)
		for action in actions {
			alertController.addAction(action)
		}
		self.present(alertController,
								 animated: true,
								 completion: nil)
	}
	
	@objc func presentOkAlertWith(title: String? = nil,
														 message: String,
														 preferredStyle: UIAlertController.Style = .alert,
														 handler: AlertActionHandler? = nil) {
		guard Thread.isMainThread else {
			DispatchQueue.main.async(execute: {
				self.presentOkAlertWith(
					title: title,
					message: message,
					handler: handler)
			})
			return
		}
		presentAlertWith(
			title: title,
			message: message,
			actions: [UIAlertAction.okay(handler: handler)])
	}
	
	@objc func presentOkCancelAlertWith(title: String? = nil,
																	 message: String,
																	 preferredStyle: UIAlertController.Style = .alert,
																	 okActionHandler: AlertActionHandler? = nil,
																	 cancelActionHandler: AlertActionHandler? = nil) {
		guard Thread.isMainThread else {
			DispatchQueue.main.async(execute: {
				self.presentOkCancelAlertWith(
					title: title,
					message: message,
					okActionHandler: okActionHandler,
					cancelActionHandler: cancelActionHandler)
			})
			return
		}
		presentAlertWith(
			title: title,
			message: message,
			actions: [
				UIAlertAction.okay(handler: okActionHandler),
				UIAlertAction.cancel(handler: cancelActionHandler)
			])
	}
	
	@objc func presentYesNoAlertWith(title: String? = nil,
																message: String,
																preferredStyle: UIAlertController.Style = .alert,
																yesActionHandler: AlertActionHandler? = nil,
																noActionHandler: AlertActionHandler? = nil) {
		guard Thread.isMainThread else {
			DispatchQueue.main.async(execute: {
				self.presentYesNoAlertWith(
					title: title,
					message: message,
					yesActionHandler: yesActionHandler,
					noActionHandler: noActionHandler)
			})
			return
		}
		presentAlertWith(
			title: title,
			message: message,
			actions: [
				UIAlertAction.yes(handler: yesActionHandler),
				UIAlertAction.no(handler: noActionHandler)
			])
	}
	
}