Delphi - Unable to save/load TObjectList to FileStream - class

Question

I have a TObjectList, which I am trying to write to disk. Although I end up with a file (54 bytes), when I change the FNAME property value to something really long, the size of the file never changes, and I get nil when I try to read it. I am at a loss as to what is wrong. Sorry for the long code snippet. it is easy to understand what is going on, just I can't figure out why it's not doing what I want.
type
{ Declare a new object type. }
TNewObject = class(TComponent)
private
FName: String;
public
property BizName: String read FName write FName;
constructor Create(const AName: String);
destructor Destroy(); override;
end;
Declare a Global var for my TObjectList
var
Form1: TForm1;
List: TObjectList<TNewObject>;
Declare my constructors and destructors..
constructor TNewObject.Create(const AName: String);
begin
FName := AName;
end;
destructor TNewObject.Destroy;
begin
inherited;
end;
Now add a button to create my objects...
procedure TForm1.CreateButtonClick(Sender: TObject);
var
Obj: TNewObject;
begin
{ Create a new List. }
{ The OwnsObjects property is set by default to true -- the list will free the owned objects automatically. }
List := TObjectList<TNewObject>.Create();
{ Add some items to the List. }
List.Add(TNewObject.Create('One'));
List.Add(TNewObject.Create('Two'));
{ Add a new item, but keep the reference. }
Obj := TNewObject.Create('Three');
List.Add(Obj);
end;
Now add a SAVE Button
procedure TForm1.SaveButtonClick(Sender: TObject);
var
i: Integer;
fs: TfileStream;
begin
if SaveDialog1.Execute then
begin
fs := TfileStream.Create(SaveDialog1.FileName, fmCreate);
try
for i := 0 to List.Count - 1 do
begin
ShowMessage(List[i].BizName);
fs.WriteComponent(TNewObject(List[i]));
end;
finally
fs.Free;
end;
end;
end;
CAVEATS: I know that only PUBLIC properties will be saved... which should be BIZNAME. The 3 entries do show up in the SHOWMESSAGE when it is being saved....
I did remember my Class Registration.
Initialization
RegisterClass(TNewObject);
For completeness sake, here is my Load Routine as well...
procedure TForm1.LoadButtonClick(Sender: TObject);
var
i: Integer;
fs: TfileStream;
vRecord: TNewObject;
begin
if OpenDialog1.Execute then
begin
List.Clear; // clear list
fs := TfileStream.Create(OpenDialog1.FileName, fmopenRead);
try
while fs.Position < fs.size do
begin
vRecord := TNewObject(fs.ReadComponent(nil));
ShowMessage(vRecord.FName);
List.Add(vRecord);
end;
finally
fs.Free;
end;
ShowMessage(IntToStr(List.Count));
end;
end;
Thank you for your help.

Answer 1

Component streaming system only streams published properties, you need to publish 'BizName'.
Alternatively you can override DefineProperties to decide what else to stream.
type
TNewObject = class(TComponent)
private
FName: String;
procedure ReadName(Reader: TReader);
procedure WriteName(Writer: TWriter);
protected
procedure DefineProperties(Filer: TFiler); override;
public
property BizName: String read FName write FName;
...
procedure TNewObject.ReadName(Reader: TReader);
begin
FName := Reader.ReadString;
end;
procedure TNewObject.WriteName(Writer: TWriter);
begin
Writer.WriteString(FName);
end;
procedure TNewObject.DefineProperties(Filer: TFiler);
begin
inherited;
Filer.DefineProperty('bizname', ReadName, WriteName, FName <> '');
end;