UIViewController and inheritance - ios

Question

I have multiple view controllers in my application. And in each of them I have to show alerts based on some conditions. Instead of adding alert controllers in each of them, I tried using inheritance as follows.
UIExtension.swift
class UIExtension: UIViewController {
func prepareAlert(title: String, message: String) -> UIAlertController {
let alert = UIAlertController(title: title, message: message, preferredStyle: UIAlertControllerStyle.alert)
alert.addAction(UIAlertAction(title: "Ok", style: .default, handler: nil))
return alert
}
}
FirstViewController.swift
class FirstViewController: UIExtension {
//somewhere inside used the following
present(prepareAlert(title: "Error Validation", message: "invalid fields"), animated: true, completion: nil)
}
Similarly, used UIExtension in other viewcontrollers to show alerts. Is this way recommended?

Answer 1

For something like this, you are better off adding your prepareAlert method to a UIViewController extension. No subclassing required.
extension UIViewController {
func prepareAlert(title: String, message: String) -> UIAlertController {
let alert = UIAlertController(title: title, message: message, preferredStyle: UIAlertControllerStyle.alert)
alert.addAction(UIAlertAction(title: "Ok", style: .default, handler: nil))
return alert
}
}
Then your view controller:
class FirstViewController: UIViewController {
//somewhere inside used the following
present(prepareAlert(title: "Error Validation", message: "invalid fields"), animated: true, completion: nil)
}
This allows you to use prepareAlert from any view controller include UITableViewController, UICollectionViewController, etc.

Answer 2

The approach is technically correct, although if you consider extending all UIViewController instances, regardless of any conditions, then it's more handy to extend it directly:
extension UIViewController {
func prepareAlert(title: String, message: String) -> UIAlertController {
let alert = UIAlertController(title: title, message: message, preferredStyle: UIAlertControllerStyle.alert)
alert.addAction(UIAlertAction(title: "Ok", style: .default, handler: nil))
return alert
}
}
rmaddy was faster. But I decided not to delete the answer, but add another idea.
Another approach is to use protocol as a wrapper for certain functionality, and this is also widely used.
Say, you have a protocol, associated with some functionality, like generating alert, in this case:
protocol Alertable {} // or whatever else name
extension Alertable {
func prepareAlert(title: String, message: String) -> UIAlertController {
let alert = UIAlertController(title: title, message: message, preferredStyle: UIAlertControllerStyle.alert)
alert.addAction(UIAlertAction(title: "Ok", style: .default, handler: nil))
return alert
}
}
Then, whenever you want certain UIViewController instance (or any other class, you get the idea) to be associated with this functionality, simply do:
class FirstViewController: UIViewController, Alertable {
// Now you can do the same:
present(prepareAlert(title: "Error Validation", message: "invalid fields"), animated: true, completion: nil)
}
To sum up, making up a protocol and extending it, and then associating certain classes with it - to expose that functionality - is a very handy and useful practice. In particular, this is a good way to encapsulate some functionality, for example, if you don't mean global/class-wide access to it.

Answer 3

Some extension method I am sharing with you that is used frequently in most application you can use it in any where of UIViewController class and enjoy :)
extension UIViewController {
let kAPPNAME = "Your App name"
func showOkAlert(_ msg: String) {
let alert = UIAlertController(title:
kAPPNAME, message: msg, preferredStyle: .alert)
let okAction = UIAlertAction(title: "OK", style: .default, handler: nil)
alert.addAction(okAction)
present(alert, animated: true, completion: nil)
}
func showOkAlertWithHandler(_ msg: String,handler: #escaping ()->Void){
let alert = UIAlertController(title: kAPPNAME, message: msg, preferredStyle: .alert)
let okAction = UIAlertAction(title: "OK", style: .default) { (type) -> Void in
handler()
}
alert.addAction(okAction)
present(alert, animated: true, completion: nil)
}
func showAlertWithActions(_ msg: String,titles:[String], handler:#escaping (_ clickedIndex: Int) -> Void) {
let alert = UIAlertController(title: kAPPNAME, message: msg, preferredStyle: .alert)
for title in titles {
let action = UIAlertAction(title: title, style: .default, handler: { (alertAction) in
//Call back fall when user clicked
let index = titles.index(of: alertAction.title!)
if index != nil {
handler(index!+1)
}
else {
handler(0)
}
})
alert.addAction(action)
}
present(alert, animated: true, completion: nil)
}
func showOkCancelAlertWithAction(_ msg: String, handler:#escaping (_ isOkAction: Bool) -> Void) {
let alert = UIAlertController(title: kAPPNAME, message: msg, preferredStyle: .alert)
let okAction = UIAlertAction(title: "OK", style: .default) { (action) -> Void in
return handler(true)
}
let cancelAction = UIAlertAction(title: "Cancel", style: .cancel) { (action) -> Void in
return handler(false)
}
alert.addAction(cancelAction)
alert.addAction(okAction)
present(alert, animated: true, completion: nil)
}
}
USES
class FirstViewController: UIViewController {
override func viewDidLoad() {
super.viewDidLoad()
//Only Info
self.showOkAlert("Hello")
//Info with Okay button
self.showOkAlertWithHandler("Hello Again") {
print("Tap to Okay")
}
//Show alert with Okay and cancel
self.showOkCancelAlertWithAction("Hello with Cancel") { (isOk) in
if isOk {
print("Okay")
}
else {
print("Cancel")
}
}
//Show alert with actions
self.showAlertWithActions("Hello with action", titles: ["Allow","Don't Allow", "Cancel"]) { (tapIndex) in
if tapIndex == 1 {
print("Allow")
}
}
}
}