Delphi: Store data in somekind of structure

Question

For a simulation program I\'m working in Delphi 2010. The simulation isn\'t a problem but I need to use large collection of data which gives a problem. The data is available

Answer 1

Add SaveToStream() and LoadFromStream() methods to your data object which, well, save the data to a stream and load data from a stream.

type
  TMyData = class(TObject)
  private
    FChildProducts: TList;
    FProductnumber : integer;
    FClean: boolean;
  public
    procedure LoadFromStream(const aStream: TStream);
    procedure SaveToStream(const aStream: TStream);
  published
    property Productnumber: Integer read FProductnumber write FProductnumber;
    property Clean: Boolean reas FClean write FClean;
  end;

procedure TMyData.LoadFromStream(const aStream: TStream);
var x, cnt: Integer;
    cD: TMyData;
begin
  aStream.Read(FProductnumber, SizeOf(FProductnumber));
  aStream.Read(FClean, SizeOf(FClean));
  // read number of child products
  aStream.Read(cnt, SizeOf(cnt));
  // load child objects
  for x := 1 to cnt do begin
     cD := TMyData.create;
     cD.LoadFromStream(aStream);
     FChildProducts.Add(cD);
  end; 
end;

procedure TMyData.SaveToStream(const aStream: TStream);
var x: Integer;
begin
  aStream.Write(FProductnumber, SizeOf(FProductnumber));
  aStream.Write(FClean, SizeOf(FClean));
  // save number of child products
  x := FChildProducts.Count;
  aStream.Write(x, SizeOf(x));
  // save child objects
  for x := 0 to FChildProducts.Count - 1 do
     (FChildProducts[x] as TMyData).SaveToStream(aStream);
end;

I assume you have some list of "root objects" so you can make an function or method which saves/loads them to/from stream ie

function SaveDataList(const List: TList;const aFileName: string);
var x: Integer;
    FS: TFileStream;
begin
  FS := TFileStream.Create(aFileName, ...);
  try
     // save file version
     x := 1;
     FS.Write(x, SizeOf(x));
     // save number of products
     x := List.Count;
     FS.Write(x, SizeOf(x));
     // save objects
     for x := 0 to List.Count - 1 do
       (List[x] as TMyData).SaveToStream(FS);
  finally
     FS.Free;
  end;
end;

This is the general idea... how to load data back should be clear too. The file version thing is there so that when the data object changes (ie you add some property) you can increment the version number so that in the loading code you can load data into right version of the data object.