existItem method
API to check the item is existing or not.
Parameters:
id ID to be checked item.
Return 'true', if there is item.
Exceptions:
Throws an ArgumentError if the ID is empty.
Implementation
bool existItem(String id) {
if (id.isEmpty) {
throw ArgumentError("existItem : You must set ID.");
}
if (_getIndex(0, id) > -1) {
return true;
} else {
return false;
}
}