presentViewController not working in Swift - ios

Question

Thank you for reading this. I would like to have a functions Swift file where I put all of the functions for my project into, that the other Swift files could call. I am trying to create an alert function in the functions file that, when I pass in a specific string, it shows a specific alert. It was working when it was in the main file, but when I moved it to the functions file, presentViewController is giving me an error, saying "Use of unresolved identifier 'presentViewController'." Please help! Here is my code:
in the functions file:
import Foundation
import UIKit
/**********************************************
Variables
***********************************************/
var canTapButton: Bool = false
var tappedAmount = 0
/**********************************************
Functions
***********************************************/
//the alert to ask the user to assess their speed
func showAlert(alert: String) -> Void
{
if(alert == "pleaseAssessAlert")
{
let pleaseAssessAlert = UIAlertController(title: "Welcome!", message: "If this is your firs time, I encourage you to use the Speed Assessment Tool (located in the menu) to figure which of you fingers is fastest!", preferredStyle: .Alert)
//ok button
let okButtonOnAlertAction = UIAlertAction(title: "Done", style: .Default)
{ (action) -> Void in
//what happens when "ok" is pressed
}
pleaseAssessAlert.addAction(okButtonOnAlertAction)
presentViewController(pleaseAssessAlert, animated: true, completion: nil)
}
else
{
println("Error calling the alert function.")
}
}
Thanks!

Answer 1

The presentViewController is the instance method of UIViewController class. So you can't access it on your function file like this.
You should change the function like:
func showAlert(alert : String, viewController : UIViewController) -> Void
{
if(alert == "pleaseAssessAlert")
{
let pleaseAssessAlert = UIAlertController(title: "Welcome!", message: "If this is your firs time, I encourage you to use the Speed Assessment Tool (located in the menu) to figure which of you fingers is fastest!", preferredStyle: .Alert)
//ok button
let okButtonOnAlertAction = UIAlertAction(title: "Done", style: .Default)
{ (action) -> Void in
//what happens when "ok" is pressed
}
pleaseAssessAlert.addAction(okButtonOnAlertAction)
viewController.presentViewController(pleaseAssessAlert, animated: true, completion: nil)
}
else
{
println("Error calling the alert function.")
}
}
Here, you are passing a UIViewController instance to this function and calling the presentViewController of that View Controller class.

Answer 2

In Swift 3:
The method presentViewController is replaced by present.
You can use it like the old one:
self.present(viewControllerToPresent, animated: true, completion: nil)

Answer 3

First, you need to check your NavigationController is appropriate or not?
If Yes, then Here is code for present and dismiss presentviewcontroller
For presenting PresentViewController :
let next = self.storyboard?.instantiateViewControllerWithIdentifier("Your view controller identifier") as! Yourviewcontroller
self.presentViewController(next, animated: true, completion: nil)
Dismiss Presentviewcontroller
self.dismissViewControllerAnimated(true, completion: nil)

Answer 4

I would say go with MidHun MP method above but, if you are looking for another way to do this without bringing in the UIViewController then:
func showAlert(alert : String) {
var window: UIWindow?
if(alert == "pleaseAssessAlert")
{
let pleaseAssessAlert = UIAlertController(title: "Welcome!", message: "If this is your firs time, I encourage you to use the Speed Assessment Tool (located in the menu) to figure which of you fingers is fastest!", preferredStyle: .Alert)
//ok button
let okButtonOnAlertAction = UIAlertAction(title: "Done", style: .Default)
{ (action) -> Void in
//what happens when "ok" is pressed
}
pleaseAssessAlert.addAction(okButtonOnAlertAction)
self.window?.rootViewController?.presentViewController(pleaseAssessAlert, animated: true, completion: nil)
}
else
{
println("Error calling the alert function.")
}
}

Answer 5

Presenting & navigation view controller has a problem with layoutsubviews function while using self.view or viewcontroller.view, so one must avoid those function.
Check:
func layoutsubviews not allows to provide the viewcontroller.view to work on it