How to implement passcode logic to the screen

Question

Hello i am creating Swift app and i want to make a screen similar to passcode lock in iphone in which we can add numbers in the textfield by pressing buttons. The problem is that i am not able to get the logic for the specific layout.

this is how the layout looks :-

the grey boxes are UITextFields and light blue are buttons.

Below is the code so far:-

@IBOutlet var numberPadButtons: [UIButton]!
   
@IBOutlet var txtFields: [UITextField]! 

@IBAction func numbPadBtnsTapped(_ sender: UIButton) {
        //Unable to implement the logic
    }

buttons and textfields have tags (0-10 & 1 to 4).

Answer 1

[Update Answer]

Basic Passcode Logic in Swift

@IBOutlet var txtfields: [UITextField]!
var passcode:[String] = [] //["1","3","5","0"]
var limit = 4

@IBAction func PressOnBtn(_ sender: UIButton) {
    if sender.tag > 10
    {
        if passcode.count > 0
        {
            self.passcode.removeLast()
            self.txtfields[self.passcode.count].text = ""
        }
    }
    else
    {
        if limit == passcode.count
        {
            return
        }
        self.passcode.append("\(sender.tag)")
        self.filltextfiled()
    }
}

func filltextfiled()
{
    for (index,pass) in self.passcode.enumerated()
    {
        self.txtfields[index].text = pass
    }
    
}