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Streaming Components (Views: 100)


Problem/Question/Abstract:

Saving and loading Component Published Propertys to disk

Answer:

The TStreams Class has a nice feature Couse it can stream component propertys in just one line .

So here's the complete unit where i Stream the component
If your class is not in the same unit you will have to register it .

{
procedure RegisterClasses(AClasses: array of TPersistentClass);

Description

Call RegisterClasses to register a set of custom classes in a single line. Each class is registered by calling RegisterClass. Unregistered classes can’t be loaded or saved by the VCL streaming system.
}

unit Unit1;

interface

uses
  Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs,
  StdCtrls;

type
  // jus a enumeration
  TSomeints = 1..10;
  // set of the enumeration
  TExampleSet = set of TSomeints;
  TExampleComponent = class(TComponent)
  private
    FASet: TExampleSet;
    FAString: string;
    FAFloat: Double;
    FAInteger: Integer;
  published
    // Anyting you want streamed and is streameble by Delphi you can publish
    // as property
    property AString: string read FAString write FAString;
    property ASet: TExampleSet read FASet write FASet;
    property AInteger: Integer read FAInteger write FAInteger;
    property AFloat: Double read FAFloat write FAFloat;
  end;

  TForm1 = class(TForm)
    SaveToStream: TButton;
    LoadFromStream: TButton;
    OpenDialog1: TOpenDialog;
    SaveDialog1: TSaveDialog;
    EAFloat: TEdit;
    EAstring: TEdit;
    procedure SaveToStreamClick(Sender: TObject);
    procedure FormCreate(Sender: TObject);
    procedure FormDestroy(Sender: TObject);
    procedure LoadFromStreamClick(Sender: TObject);
  private
    FExampleComponent: TExampleComponent;
    procedure SetExampleComponent(const Value: TExampleComponent);
    { Private declarations }
  public
    property ExampleComponent: TExampleComponent read FExampleComponent write
      SetExampleComponent;
    procedure ObjectToGui;
    procedure GuiToObject;
    { Public declarations }
  end;

var
  Form1: TForm1;

implementation

{$R *.DFM}

procedure TForm1.SaveToStreamClick(Sender: TObject);
var
  AStream: TMemoryStream;
begin
  if SaveDialog1.execute then
  begin
    GuiToObject;
    AStream := TMemoryStream.Create;
    try
      AStream.WriteComponent(ExampleComponent);
      AStream.SaveToFile(SaveDialog1.FileName);
    finally
      AStream.free;
    end;
  end;
end;

procedure TForm1.SetExampleComponent(const Value: TExampleComponent);
begin
  FExampleComponent := Value;
end;

procedure TForm1.FormCreate(Sender: TObject);
begin
  // this is the Procedure To Call if you want to Use components not defined
  // in this unit ;
  // RegisterClasses([TButton,TMemo,TEnz]);
  FExampleComponent := TExampleComponent.Create(Self);
end;

procedure TForm1.FormDestroy(Sender: TObject);
begin
  FExampleComponent.free;
end;

procedure TForm1.LoadFromStreamClick(Sender: TObject);

var
  AStream: TMemoryStream;
begin
  if OpenDialog1.execute then
  begin
    AStream := TMemoryStream.Create;
    try
      AStream.LoadFromFile(OpenDialog1.FileName);
      AStream.ReadComponent(ExampleComponent);
      ObjectToGui;
    finally
      AStream.free;
    end;
  end;
end;

procedure TForm1.GuiToObject;
begin
  ExampleComponent.AString := EAstring.Text;
  ExampleComponent.AFloat := StrToFloat(EAFloat.Text);
end;

procedure TForm1.ObjectToGui;
begin
  EAstring.Text := ExampleComponent.AString;
  EAFloat.Text := FloatToStr(ExampleComponent.AFloat);
end;

end.

Component Download: http://www.xs4all.nl/~suusie/Pieter/Programs/StreamingComponent.zip

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