Accessing elements from another view controller comes up nil - ios

Question

I have an alert view that i made using presentr from GitHub. I used a simple view controller that will overlay over the current view controller. Now i have elements such as a UIImage and a UIlabel from the first view controller that needs to be accessed by the alert view controller. But when I click a unbutton in the alert view controller to access the uiimage and text from uilabel from the firstviewcontroller. Here is the code. Can you show me how I can fix this. I can't segue the data because I'm presenting the view controller and the data I'm trying to access is too much too segue anyway. I keep getting this error "fatal error: unexpectedly found nil while unwrapping an Optional value" overtime i click the save button in alertviewcontroller.
class firstviewcontroller: UIViewController{
var photos2: [ImageSource]?
#IBOutlet weak var Label: UIlabel!
#IBOutlet weak var Image: UIImage!
}
class alertviewcontroller: UIViewController{
#IBAction func Save(_ sender: Any) {
dismiss(animated: true, completion: nil)
let storyboard: UIStoryboard = UIStoryboard.init(name: "Main", bundle: nil)
let firstViewController: firstviewcontroller = storyboard.instantiateViewController(withIdentifier: "firstviewcontroller") as! firstviewcontroller
if let image = firstViewController.Image {
imageview.image = image
}
if let label = firstViewController.Label {
label.text = Label.text
}
}
}

Answer 1

The biggest mistake you're making is that you are creating a new instance of firstviewcontroller instead of just accessing the current one.
class alertviewcontroller: UIViewController{
#IBAction func Save(_ sender: Any) {
dismiss(animated: true, completion: nil)
let storyboard: UIStoryboard = UIStoryboard.init(name: "Main", bundle: nil)
let firstViewController: firstviewcontroller = storyboard.instantiateViewController(withIdentifier: "firstviewcontroller") as! firstviewcontroller // This is the mistake
if let image = firstViewController.Image {
imageview.image = image
}
if let label = firstViewController.Label {
label.text = Label.text
}
}
}
What you should do instead is access the presentingViewController since you presented the alertviewcontroller using the present function
The code would look like this
class alertviewcontroller: UIViewController{
#IBAction func Save(_ sender: Any) {
dismiss(animated: true, completion: nil)
let storyboard: UIStoryboard = UIStoryboard.init(name: "Main", bundle: nil)
// NOTE: only do implicit unwrapping `as!` if you're sure that the value you're unwrapping is not `nil` or it is of the correct `data type` cause it might cause your app to crash
let firstViewController: firstviewcontroller = self.presentingViewController as! firstviewcontroller
if let image = firstViewController.Image {
imageview.image = image
}
if let label = firstViewController.Label {
label.text = Label.text
}
}
}
Tip: Please review Swift coding guidelines since there are some minor mistakes regarding your naming of methods, variables, and classes.

Answer 2

Might I am wrong but after review your code I have found this messing statement
let firstViewController: firstviewcontroller = storyboard.instantiateViewController(withIdentifier: "firstviewcontroller") as! firstviewcontroller
In this statement you are creating a new instance of firstviewcontroller not accessing already created instance of firstviewcontroller.
Next, you said
I used a simple view controller that will overlay over the current
view controller
So I have assumed you didn't present or push alertviewcontroller on current viewController, on that behave I suggest you the following solutions
In alertviewcontroller get the instance of topViewController by using this method
class func topViewController(base: UIViewController? = (UIApplication.shared.delegate as! AppDelegate).window?.rootViewController) -> UIViewController? {
if let nav = base as? UINavigationController {
return topViewController(base: nav.visibleViewController)
}
if let tab = base as? UITabBarController {
if let selected = tab.selectedViewController {
return topViewController(base: selected)
}
}
if let presented = base?.presentedViewController {
return topViewController(base: presented)
}
return base
}
then you can transfer your data from alertviewcontroller to topViewController.
Next solution is that you can pass values from alertviewcontroller to firstviewcontroller by using delegates.