func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {
        if textField == mobileNumberTextField {
            guard let text = textField.text else { return false }
            // All digits entered
            let newString = (text as NSString).replacingCharacters(in: range, with: string)
            if newString.count > 12 {
                return false
            }

            let positionOriginal = textField.beginningOfDocument
            var cursorLocation: UITextPosition?
            if string != "" {
                // Add
                if range.location == 3 || range.location == 7 {
                    cursorLocation = textField.position(from: positionOriginal, offset: range.location + NSString(string: string).length + 1)
                } else {
                    cursorLocation = textField.position(from: positionOriginal, offset: range.location + NSString(string: string).length)
                }
            } else {
                // Delete
                if range.location == 4 || range.location == 8 {
                    cursorLocation = textField.position(from: positionOriginal, offset: range.location + NSString(string: string).length - 1)
                } else {
                    cursorLocation = textField.position(from: positionOriginal, offset: range.location + NSString(string: string).length)
                }
            }
            let cleanMobileNumber = newString.replacingOccurrences(of: "-", with: "")
            textField.text = cleanMobileNumber.format(mask: "XXX-XXX-XXXX")

            isMobileNumberValid = MobileValidator.isValid(cleanMobileNumber)

            if let cursorLoc = cursorLocation {
                textField.selectedTextRange = textField.textRange(from: cursorLoc, to: cursorLoc)
            }
            return false
        }
        return true
    }