Can't give parameter values to extension method UIAlertController - swift

Question

I am trying to write an extension method that generates an UIAlertController based on what you give as a parameter.
extension UIAlertController {
func generate(messageText: String, messageTitle: String, buttonText: String) {
let alert = UIAlertController(title: messageTitle, message: messageText, preferredStyle: UIAlertControllerStyle.Alert)
alert.addAction(UIAlertAction(title: buttonText, style: UIAlertActionStyle.Default, handler: nil))
self.presentViewController(alert, animated: true, completion: nil)
}
}
This doesn't give an error.
But when I try to call it and add the parameter values
var alertTest = UIAlertController.generate("")
It gives the following error: Type 'UIAlertController' does not conform to protocol 'StringLiteralConvertible'
How can I fix this?
Or isn't it possible what i am trying to achieve?

Answer 1

There are some differences between how you have defined the generate method in the extension and how you are using it.
generate is declared as a function accepting 3 string parameters and returning void.
You are calling as a static method instead, passing one parameter, and expecting a return value.
The right way of using it is like this:
var alert = UIAlertController()
alert.generate("A Message", messageTitle: "A title", buttonText: "A button label")
However I think that the method implementation is incorrect, because you are creating a new instance of UIAlertController instead of (re)using the one the method is called on. What you probably need is a static method, in which case it should look like:
extension UIAlertController {
class func generate(# parent: UIViewController, messageText: String, messageTitle: String, buttonText: String) -> UIAlertController {
let alert = UIAlertController(title: messageTitle, message: messageText, preferredStyle: UIAlertControllerStyle.Alert)
alert.addAction(UIAlertAction(title: buttonText, style: UIAlertActionStyle.Default, handler: nil))
parent.presentViewController(alert, animated: true, completion: nil)
return alert
}
}
and used as:
var alert = UIAlertController.generate(parent: self, messageText: "A Message", messageTitle: "A title", buttonText: "A button label")