Why I am getting Cannot find 'UIAlertController' in scope? error if i write alert function in separate swift file or if i use extension its not coming to another viewcontroller why?
code:
func showAlert(title: String, message: String) {
let alertController = UIAlertController(title: title, message:
message, preferredStyle: .alert)
alertController.addAction(UIAlertAction(title: "OK", style: .default, handler: {action in
}))
self.present(alertController, animated: true, completion: nil)
}
error:
Cannot find 'UIAlertController' in scope,
Cannot find 'UIAlertAction' in scope
Cannot find 'self' in scope
Probably you forgot this in your viewController:
import UIKit
so your file has no idea what UIAlertController or UIAlertAction is
if you want to create an alert view controller to be used across multiple UIViewController you can do this:
import UIKit
class CustomAlertController: NSObject {
let message:String?
let title:String?
init(title:String, message:String) {
self.message = message
self.title = title
}
func showAlert()->UIAlertController {
let alertController = UIAlertController(title: self.title, message: self.message, preferredStyle: .alert)
// you can further customize your buttons, buttons' title etc
alertController.addAction(UIAlertAction(title: "OK", style: .default, handler: {action in
}))
return alertController
}
}
then your view controllers
import UIKit
class ViewController: UIViewController {
override func viewDidLoad() {
super.viewDidLoad()
let alert = CustomAlertController(title: "Hello", message: "My message to the world")
DispatchQueue.main.async {
self.present(alert.showAlert(), animated: true, completion: nil)
}
}
}
Is there any separate global function to add a different style and a different handler for alerts?
My function from AppDelegate looks like this:
static func showAlertView(vc : UIViewController, titleString : String , messageString: String) ->()
{
let alertView = UIAlertController(title: titleString, message: messageString, preferredStyle: .alert)
let alertAction = UIAlertAction(title: "ok", style: .cancel) { (alert) in
vc.dismiss(animated: true, completion: nil)
}
alertView.addAction(alertAction)
vc.present(alertView, animated: true, completion: nil)
}
You just need to add more parameters to your function. In the code below I've added the following: controllerStyle for UIAlertController, actionStyle for UIAlertAction and action for UIAlertAction handler.
static func showAlertView(vc : UIViewController, titleString : String , messageString: String, controllerStyle: UIAlertController.Style = .alert, actionStyle: UIAlertAction.Style = .cancel, action: #escaping () -> () = {}) {
let alertView = UIAlertController(title: titleString, message: messageString, preferredStyle: controllerStyle)
let alertAction = UIAlertAction(title: "ok", style: .cancel) { (alert) in
if action == {} {
vc.dismiss(animated: true, completion: nil)
} else {
action()
}
}
alertView.addAction(alertAction)
vc.present(alertView, animated: true, completion: nil)
}
I am presenting the UIAlertController on the main thread as :
class HelperMethodClass: NSObject {
class func showAlertMessage(message:String, viewController: UIViewController) {
let alertMessage = UIAlertController(title: "", message: message, preferredStyle: .alert)
let cancelAction = UIAlertAction(title: "Ok", style: .cancel)
alertMessage.addAction(cancelAction)
DispatchQueue.main.async {
viewController.present(alertMessage, animated: true, completion: nil)
}
}
}
And I am calling the method from any UIViewController as:
HelperMethodClass.showAlertMessage(message: "Any Message", viewController: self)
I am getting the output properly.
But in console I am getting below message:
[Assert] Cannot be called with asCopy = NO on non-main thread.
Is there something I have done wrong here or I can ignore this message ?
Edit
Thanks to #NicolasMiari :
Adding below code is not showing any message:
DispatchQueue.main.async {
HelperMethodClass.showAlertMessage(message: "Any Message", viewController: self)
}
What can be the reason that previously it was showing the message in console?
You should call all code from showAlertMessage on main queue:
class func showAlertMessage(message:String, viewController: UIViewController) {
DispatchQueue.main.async {
let alertMessage = UIAlertController(title: "", message: message, preferredStyle: .alert)
let cancelAction = UIAlertAction(title: "Ok", style: .cancel)
alertMessage.addAction(cancelAction)
viewController.present(alertMessage, animated: true, completion: nil)
}
}
The following code gives me an sigabort when .present is called:
func alert(message: String, title: String = "") {
let alertController = UIAlertController(title: title, message: message, preferredStyle: UIAlertControllerStyle.alert)
alertController.addAction(UIAlertAction(title: "Ok", style: .default, handler: { action in
switch action.style {
case .default:
print("default")
case .cancel:
print("cancel")
case .destructive:
print("destructive")
}}))
alertController.present(alertController, animated: true, completion: nil)
}
Help! I am not getting this!
You're calling the alertController's present instead of the view's. Change it to refer to the parent UIViewController's present(...).
func present(_ viewControllerToPresent: UIViewController,
animated flag: Bool,
completion: (() -> Void)? = nil)
https://developer.apple.com/documentation/uikit/uiviewcontroller/1621380-present
I have used side navigation menu(SWReveal). I have 4 ViewControllers. How can use same alertAction in different views.
You can create UIViewController extension like below:
extension UIViewController {
func showAlert(title: String?, message: String?, actionTitles:[String?], actions:[((UIAlertAction) -> Void)?]) {
let alert = UIAlertController(title: title, message: message, preferredStyle: .alert)
for (index, title) in actionTitles.enumerated() {
let action = UIAlertAction(title: title, style: .default, handler: actions[index])
alert.addAction(action)
}
self.present(alert, animated: true, completion: nil)
}
}
And you can use this alert in UIViewController like below:
showAlert(title: "Your Title", message: "Your custom Message", actionTitles: ["Ok","Cancel"], actions: [{ action1 in
//OK Action
}, { action2 in
// Cancel Action
}
])
Hope will get your solution.
You can also use like this way.
class IOSPublicDefaultAlert: NSObject{
var viewController: UIViewController?
var actionCompletion: ((String) -> ())?
var alertTitle: String?
var alertMessage : String?
var alertType: UIAlertControllerStyle?
var actionTitleAndType: [String: UIAlertActionStyle]?
init(viewController : UIViewController,alertTitle: String?,alertMessage : String?,alertType: UIAlertControllerStyle = .alert,actionTitleAndType: [String: UIAlertActionStyle] ,actionCompletion : ((String)->())?){
super.init()
self.viewController = viewController
self.actionCompletion = actionCompletion
self.alertTitle = alertTitle
self.alertMessage = alertMessage
self.alertType = alertType
self.actionTitleAndType = actionTitleAndType
showAlert()
}
func showAlert(){
let alert = UIAlertController.init(title: alertTitle, message: alertMessage, preferredStyle: self.alertType ?? .alert)
for (actionTitle, actionType) in actionTitleAndType!{
let action = UIAlertAction(title: actionTitle, style: actionType) { (action) in
if let com = self.actionCompletion{
com(actionTitle)
}
}
alert.addAction(action)
}
viewController?.present(alert, animated: true, completion: nil)
}
}
and use add where you like as below sample
_ = IOSPublicDefaultAlert.init(viewController: self, alertTitle: "Warning!!!", alertMessage: alertMessage, actionTitleAndType: ["Ok" : .destructive, "Cancel" : .default], actionCompletion: { [unowned self] (title) in
if title == "Ok"{
}
})
In swift, your project, you can create a new .swift file and in this file create a class:
import UIKit
import Foundation
class yourFileName {
//Create a class function alerview
class func displayAlert(title: String, withMessage msg: String, andbtnTitle btntitle: String, in vc: UIViewController) {
let alert = UIAlertController(title: title, message: msg, preferredStyle: .alert)
alert.addAction(UIAlertAction(title: btntitle, style: UIAlertActionStyle.default, handler: nil))
appDelegate.window?.rootViewController?.present(alert, animated: true, completion: nil)
}
}
//and now your any ViewController.swift file or any other file in your project you can access alert following way.
class viewController: UIViewController {
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view, typically from a nib.
yourfilename.displayAlert(title: "Alert", withMessage msg: "my alert view display", andbtnTitle btntitle: "Ok", in vc: self) // access your alertview
}
}
I hope it's work for you.
Create BaseController with a method that can show alert.
//Copyright © 2017 dip. All rights reserved.
import UIKit
class BaseController: UIViewController {
override func viewDidLoad() {
super.viewDidLoad()
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
///This is common method to show alert with same action
func showAlert() {
let alert = UIAlertController(title: "Alert", message: "my msg on alert", preferredStyle: .alert)
alert.addAction(UIAlertAction(title: "OK", style: .default, handler: { (action) in
///This will be common alert ok aciton for all child controllers.
print("Do some userful common work..")
}))
self.present(alert, animated: true, completion: nil)
}
}
Inherit Your 4 controllers from BaseController
// Copyright © 2017 dip. All rights reserved.
//
import UIKit
class ChildVC: BaseController {
override func viewDidLoad() {
super.viewDidLoad()
//call show alert when ever you wish
///This method will call showAlert() method on super class (BaseController)
self.showAlert()
}
}
Call self.showAlert() method from child when you want show alert with common action.
// MARK: - Alertable View
protocol AlertableView {
// Use handler if need catch cancel alert action
typealias CompletionHandler = (() -> Void)
func displayAlert(with title: String, message: String, actions: [UIAlertAction]?)
func displayAlert(with title: String, message: String, style: UIAlertControllerStyle, actions: [UIAlertAction]?, completion: CompletionHandler?)
}
extension AlertableView where Self: UIViewController {
func displayAlert(with title: String, message: String, actions: [UIAlertAction]?) {
self.displayAlert(with: title, message: message, style: .alert, actions: actions, completion: nil)
}
func displayAlert(with title: String, message: String, style: UIAlertControllerStyle, actions: [UIAlertAction]?, completion: CompletionHandler?) {
let alertCancelAction = UIAlertAction(title: "Cancel".localized, style: .cancel) { (action) in
guard let completion = completion else { return }
completion()
}
let alertController = UIAlertController(title: title, message: message, preferredStyle: style)
if let actions = actions {
for action in actions {
alertController.addAction(action)
}
alertController.addAction(alertCancelAction)
} else {
// If not any custom actions, we add OK alert button
let alertOkAction = UIAlertAction(title: "OK".localized, style: .cancel) { (action) in
guard let completion = completion else { return }
completion()
}
alertController.addAction(alertOkAction)
}
self.present(alertController, animated: true, completion: nil)
}
}
Create a common function ,
import UIKit
class AlertClass: NSObject {
func showAlertWithVC(_ VC : UIViewController, andMessage message: String ){
DispatchQueue.main.async {
let alert = UIAlertController(title: "APPLICATION_NAME", message: message , preferredStyle: UIAlertControllerStyle.alert)
alert.addAction(UIAlertAction(title: "Ok", style: UIAlertActionStyle.default, handler: nil))
VC.present(alert, animated: true, completion: nil)
}
}
}
Simply call AlertClass().showAlertWithVC() where you want to show Alert.