removeItem method
API to remove item.
Parameters:
id - ID of item to remove.
Exceptions:
Throws an ArgumentError if the ID is empty.
Throws an ArgumentError if the ID is invalid.
Implementation
void removeItem(String id){
int index;
if (id.isEmpty) {
throw ArgumentError("removeItem : You must set itemId.");
}
else if ((index = _getItemIndex(id)) < 0) {
throw ArgumentError("removeItem : there is no id.");
}
items?.removeAt(index);
}