validateExpiration method
Implementation
bool validateExpiration(String _month, String _year) {
var month = int.tryParse(_month);
var year = int.tryParse(_year);
if (month == null || year == null) return false;
if (0 == month) return false;
if (month > 12 || 1 > month) return false;
if (0 == year) return false;
var today = DateTime.now();
if (2 == _year.length) {
year = int.tryParse("${today.year.toString().substring(0, 2)}$year");
}
if (year == null || year < today.year) return false;
if (year == today.year) {
if (month > 12 || month < today.month + 1) return false;
} else if (year > today.year && (month > 12 || 1 > month)) return false;
return true;
}