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Streaming Published Properties

Posted on 2002-06-29
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Last Modified: 2010-04-04
I'm experimenting with saving and loading components using Delphi's streaming mechanism. I've declared a new class with the following declaration :

TOmxSourceID   = type integer;
TOmxClassID    = type integer;

TOmxSourceClass = class(TPersistent)
private
  FClass: TOmxClassID;
  FSource: TOmxSourceID;
published
  property Source : TOmxSourceID read FSource write FSource;
  property SourceClass : TOmxClassID read FClass write FClass;
end;

I have then declared a new panel component with TomxSourceClass as a published property

TOmxDataEntryPanel = class(TPanel)
private
  FSourceClass: TOmxSourceClass;
public
  constructor Create(AOwner : TComponent); override;
published
  property SourceClass : TOmxSourceClass read FSourceClass;
end;

constructor TOmxDataEntryPanel.Create(AOwner: TComponent);
begin
  inherited;
  FSourceClass := TOmxSourceClass.Create;
  FSourceClass.Source := -1;
  FSourceClass.SourceClass  := -1;
end;

The SourceClass.Source and SourceClass.SourceClass properties can be set OK but when the form is saved to a database and reloaded the properties have defaulted back to -1. I don't think the problem is with the save/load routines as all the other properties are saved ok.

Could it be the declarations of TomxSourceID and TomxClassID?

Thanks

Jo
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Comment
Question by:nnbbb09
2 Comments
 
LVL 3

Author Comment

by:nnbbb09
ID: 7120369

I've managed to answer it myself. The problem was due to SourceClass being declared as a readonly property of TomxPanel. It should read

TOmxDataEntryPanel = class(TPanel)
private
 FSourceClass: TOmxSourceClass;
public
 constructor Create(AOwner : TComponent); override;
published
 property SourceClass : TOmxSourceClass read FSourceClass write FSourceClass;
end;
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