getValue method
API to get value for ID.
Parameters:
id Unique ID to get value.
Return double value
Exceptions:
Throws an ArgumentError if the ID is empty.
Throws an ArgumentError if the ID is invalid.
Implementation
double? getValue(String id)
{
if (id.isEmpty) {
throw ArgumentError("You must set itemId.");
}
final index = items!.indexWhere((items) => items.id == id);
if (index > -1) {
return items!.elementAt(index).dValue;
}
throw ArgumentError("id is invalid.");
}