Unable to pass on or retrieve data to another class - swift

Question

Trying to create a custom drop-down and facing issues in passing on data and retrieving the user selection from the custom drop-down. The solution however works when I use static var.
In the below code, I have a viewController class from where I am programmatically calling a popOver.
let countryDropDown = customDropdown()
#IBAction func btMultiCountry(_ sender: Any) {
ViewController.countryDropDown.removeAll() //fuction to clear the array before load
for c in g.country{ //Array from which all items are loaded on the custom dropdown
countryDropDown.addItems(labelText: c.countryName!, toggleState: 1) //passing the values in the add function to update the Array
}
countryDropDown.showDropdown(btMultiCountry) //programatically calling the function to display popover that has the collection view with the countries as items.
}
class customDropdown: NSViewController {
#IBOutlet weak var cvDropDown: NSCollectionView!
var pop = NSPopover() // if I put static var, the popover closes with the OK button as required, however, without static the OK button doest do anything
var dropDownLabelText = [String]() //if I put static var, the values are shown on the collection view without any issue. Without static the array is blank that was load from additems function
var dropDownToggle = [Int]() // same as above
var selectedItemsIndex: [Int] {
var a = [Int]()
for (i,t) in dropDownToggle.enumerated() {
if t == 1 {
a.append(i)
print(a)
}
}
return a
}
func showDropdown(_ sender: NSButton){
let storyboard = NSStoryboard(name: NSStoryboard.Name("Main"), bundle: nil)
let VC = storyboard.instantiateController(withIdentifier: "dropDownForm") as? customDropdown
pop.contentViewController = VC
pop.behavior = NSPopover.Behavior.transient
pop.show(relativeTo: sender.bounds, of: sender, preferredEdge: NSRectEdge.minY)
print(pop)
}
#IBAction func btOK(_ sender: Any) { //this function does not close the popover if there is not static mention above
pop.close()
}
I tried putting static when declaring the variables and it worked. I do not want static and want to create different instances of the class that gives me selectedItemsIndex
For eg:
let countryDropDown = customDropdown()
let personDropDown = customDropdown()
I should be able to get a different values for countryDropDown.selectedItemsIndex and personDropDown.selectedItemsIndex
Any help is appreciated.