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procedure TaClass.SaveToStream(var s : TFilestream);
var
  i : Integer;
begin
  if s = nil then
    exit;

  //Teil 1: Eigene Daten
  s.Write(aVar, sizeOf(aVar));
  s.Write(anotherVar, sizeOf(anotherVar));

  //Teil 2: Daten von Fremdkomponenten
  for i:=0 to High(subObjects) do
    subObjects[i].SaveToStream(s);
end;

procedure TaClass.LoadFromStream(var s : TFilestream);
var
  i : Integer;
begin
  if s = nil then
    exit;

  //Teil 1: Eigene Daten
  s.Read(aVar, sizeOf(aVar));
  s.Read(anotherVar, sizeOf(anotherVar));

  //Teil 2: Daten von Fremdkomponenten
  for i:=0 to High(subObjects) do
    subObjects[i].LoadFromStream(s);
end;                    

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unit Unit2;

interface

uses
  SysUtils, Classes;

type
  TMyClass = class(TObject)
  private
    FValueA: String;
    FValueB: Integer;
    procedure SaveValues(AFiler: TWriter);
    procedure LoadValues(AFiler: TReader);
  public
    property ValueA: String read FValueA write FValueA;
    property ValueB: Integer read FValueB write FValueB;
  end;

  TMyObject = class(TObject)
  private
    FMyClass: TMyClass;
  public
    constructor Create;
    destructor Destroy; override;
    procedure SaveToFile(const FileName: String);
    procedure LoadFromFile(const FileName: String);
    property MyClass: TMyClass read FMyClass write FMyClass;
  end;

implementation

{ TMyClass }

procedure TMyClass.LoadValues(AFiler: TReader);
begin
  FValueA := AFiler.ReadString;
  FValueB := AFiler.ReadInteger;
end;

procedure TMyClass.SaveValues(AFiler: TWriter);
begin
  AFiler.WriteString(FValueA);
  AFiler.WriteInteger(FValueB);
end;

{ TMyObject }

constructor TMyObject.Create;
begin
  inherited;
  FMyClass := TMyClass.Create;
end;

destructor TMyObject.Destroy;
begin
  FMyClass.Free;
  inherited;
end;

procedure TMyObject.LoadFromFile(const FileName: String);
var
  Handle: Integer;
  Stream: THandleStream;
  Filer: TReader;
begin
  Handle := FileOpen(FileName, fmOpenRead);
  if Handle <> -1 then
  begin
    Stream := THandleStream.Create(Handle);
    Filer := TReader.Create(Stream, 4096);
    try
      Filer.ReadSignature;
      if Filer.ReadIdent = ClassName then
        MyClass.LoadValues(Filer);
    finally
      Filer.Free;
      Stream.Free;
      FileClose(Handle);
    end;
  end;
end;

procedure TMyObject.SaveToFile(const FileName: String);
var
  Handle: Integer;
  Stream: THandleStream;
  Filer: TWriter;
begin
  Handle := FileCreate(FileName);
  if Handle <> -1 then
  begin
    Stream := THandleStream.Create(Handle);
    Filer := TWriter.Create(Stream, 4096);
    try
      Filer.WriteSignature;
      Filer.WriteIdent(ClassName);
      FMyClass.SaveValues(Filer);
    finally
      Filer.Free;
      Stream.Free;
      FileClose(Handle);
    end;
  end;
end;

end.                    

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procedure TCircuitElementGroup.SaveToStream(var AStream: TFileStream);
var
  i: Integer;
begin
  inherited;
  i := Length(FElements);
  AStream.Write(i, SizeOf(i)); //Write number of subelements
  AStream.Write(FParallel, SizeOf(FParallel));
  for i := Low(FElements) to High(FElements) do //Write subelements to stream
    FElements[i].SaveToStream(AStream);
end;                    

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function LoadFromStream(var AStream: TFileStream): TCustomCircuitElement;
var
  TempID, i: Integer;
  AValue: Double;
  AName: ShortString;
  AParallel: Boolean;
begin
  Result := nil; //Initialize
  with AStream do begin
    Read(TempID, SizeOf(TempID)); //ID
    Read(AName, SizeOf(AName)); //Name
    Read(AValue, SizeOf(AValue)); //Value
    case TempID of
      1: Result := TResistor.Create(AValue);
      2: Result := TCapacitor.Create(AValue);
      3: Result := TCoil.Create(AValue);
      4: begin
           Result := TCircuitElementGroup.Create;
           Read(TempID, SizeOf(TempID)); //Read number of children
           Read(AParallel, SizeOf(AParallel));
           (Result as TCircuitElementGroup).Parallel := AParallel;
           for i := 0 to TempID - 1 do
             (Result as TCircuitElementGroup).AddElement(LoadFromStream(AStream));
         end;
      end;
    Result.Name := AName;
    end;
end;