Question

The question more or less says it all. Given the following record structure:

type
    TPerson = record
        Name: string;
        Age: Integer;
    end;
    PPerson = ^TPerson;
    TPersonList = TList<TPerson>;

Is the following code valid?

procedure ReadPeople(DataSet: TDataSet; PersonList: TPersonList);
begin
    PersonList.Count := DataSet.RecordCount;
    if DataSet.RecordCount = 0 then
        Exit;

    DataSet.First;
    while not DataSet.Eof do begin
        PersonList[DataSet.RecNo].Name := DataSet.FieldByName('Name').AsString;
        PersonList[DataSet.RecNo].Age := DataSet.FieldByName('Age').AsInteger;
        DataSet.Next;
    end;
end;

Do I have to use GetMem/FreeMem to allocate and free records an instance of TPersonList, or am I free to directly access the TPersonList entries directly? My gut says that the code should be valid, though I’m not sure if there’s any wrinkles related to record initialization or finalization.

Answer 1

Your code’s fine. When you use Tlist<T> with records, it treats them as value types, to be copied around. There’s no need to allocate pointers for them.