how to acces a variable in another class and change its value - ios

Question

I am new to Xcode and Swift so I don't know much about how it all works, but I am trying to make a pop-up view. I want a small view to pop up when I click a button. The view is a View Container (I don't know if that is the best way to do this so if not please tell me a better way to do this) and it starts out hidden then when I click a button it becomes visible. This View Container also has a button that if clicked, it will make the view hidden again.
Here is the code:
import UIKit
class ViewController: UIViewController {
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view, typically from a nib.
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
#IBOutlet weak var popUpView: UIView!
#IBAction func startButton(sender: UIButton) {
popUpView.hidden = false
}
}
import UIKit
class PopUpViewController: UIViewController {
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view.
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
override func prepareForSegue(segue:UIStoryboardSegue,
sender:AnyObject?)
{
// Get the new view controller using segue.destinationViewController.
// Pass the selected object to the new view controller.
}
#IBAction func backButton(sender: UIButton) {
ViewController().popUpView.hidden = true
}
}
When I run the app it starts fine because the start button is there and when I click it the pop up shows up but when I click the back button it gives me an error which says that in the console
Unknown class MKMapView in Interface Builder file.
fatal error: unexpectedly found nil while unwrapping an Optional value
and in line 31 ViewControler().popUpView.hidden = true
it says Thread 1: EXC_BAD_INSTRUCTION(code=EXC_I386_INVOP, subcode=0x0)
Can someone help. Thanks

Answer 1

Access popUpView variable from didPrepareForSeque method (this method gets called automatically when you segue to another view). Problem is that if you try to set value to soon (meaning, that button is not drawn on view), you will get nil error. Here is a little workaround. You use temporary variable (tmpValue) to store state of your button (to be hidden or not), so when viewDidLoad, you method will read this value and set button to hidden state as you intended.
In ViewController class declare temporary variable (must be optional):
var tmpValu:Bool?
Then in your PopUpViewController class remove this line from backButton action:
ViewController().popUpView.hidden = true
Instead, you will use prepareForSegue method, like this:
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
let destinationViewController = segue.destinationViewController as! ViewController
destinationViewController.tmpValu = true
}
Now, back in ViewController class in viewDidLoad add this code:
override func viewDidLoad() {
super.viewDidLoad()
if let value = tmpValu {
popUpView.hidden = value
}
}