iOS Swift - OTP Auto fill to multiple textfields

OTP.swift

func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {
        var nextTextfieldTag = 0
        if string.isEmpty {
            return true
        } else if string.count == 1 { // Auto fill OTP to multiple textfield
            textField.text = string
            nextTextfieldTag = textField.tag + 1
        } else if string.count == maximumDigits { // Paste OTP to multiple textfield
            var pastedOTP = string
            for tag in 1...maximumDigits {
                guard let textfield = view.viewWithTag(tag) as? UITextField else { continue }
                textfield.text = String(pastedOTP.removeFirst())
            }
            submitOTP()
        }
        
        if let nextTextfield = view.viewWithTag(nextTextfieldTag) as? UITextField {
            nextTextfield.becomeFirstResponder()
        } else {
            if nextTextfieldTag > maximumDigits { submitOTP() }
            view.endEditing(true)
        }
        return false
    }