How to replace array values with new value in same index in swift

I am showing dropdown in tableview cell here if i select one value from from dropdown i need to replace that selected value in existing array index

for eg: i got array like this

before array ----- ["12-R", "14-R", "13-R"]

here is my dropdown button code: initially here arrSelectedRowsBuyNew

func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCell(withIdentifier: "EventslistPopupCell", for: indexPath) as! EventslistPopupCell
cell.actionBlock = { tapAct in
    self.showDropDown(with: strArray, from: tapAct) { (item, index) in
        
        cell.dropdownTF.text = item
        
        if index == 0{
            self.arrSelectedRowsBuyNew.append(self.popupData[indexPath.row].selectedID.description + "-" + "R")
        }
        if index == 1{
            self.arrSelectedRowsBuyNew.append(self.popupData[indexPath.row].selectedID.description + "-" + "V")
        }
        
        print("after array \(self.arrSelectedRowsBuyNew)")
    }
}
return cell
}

for above code o/p: here i need to replace "12-R" with "12-V" and "14-R" with "14-V" here how to check the index and replace the new value

NOTE: here first two digits will be same for old and new array. so can we check and replace with that. first two digits coming from this self.popupData[indexPath.row].selectedID

please do help got stuck here from long time

> after array ["12-R", "14-R", "13-R", "14-V", "12-V"]

EDIT:

before replace array before array ----- ["12-R", "14-R"]

initially all values at index 0

now if i select value from first cell dropdown then its replacing like this

error:

>["12-R", "12-V"]

but i need like ["12-V", "14-R"]

I'm not sure I fully understand your question but I think you need to replace the line:

self.arrSelectedRowsBuyNew.append(self.popupData[indexPath.row].selectedID.description + "-" + "A")

with:

self.arrSelectedRowsBuyNew[index] = self.popupData[indexPath.row].selectedID.description + "-" + "A"

Your use of append is adding the new value to the array. If you want to replace a value then simply assign a new value at the desired index.