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Add controls to a form at runtime and stream the result to a file (Views: 101)


Problem/Question/Abstract:

Is it possible to add controls to a form at runtime, then stream the result to single file, thus preserving all changes for next application run?

Answer:

Yes, with some caveats. You need to register all control classes that are used on the form plus all that the user may add at runtime. Here is a little example:

unit Unit1;

interface

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

type
  TForm1 = class(TForm)
    Button1: TButton;
    Button2: TButton;
    procedure Button1Click(Sender: TObject);
    procedure Button2Click(Sender: TObject);
    procedure FormCreate(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  Form1: TForm1;

implementation

{$R *.DFM}

const
  formdata = 'formdata.bin';

procedure TForm1.Button1Click(Sender: TObject);
begin
  with TEdit.Create(self) do
  begin
    left := button1.Left + button1.width + 10;
    top := button1.top;
    Name := 'NewEdit';
    parent := self;
  end;
end;

procedure TForm1.Button2Click(Sender: TObject);
var
  fs: TFileStream;
begin
  fs := TFileStream.Create(ExtractFilePath(ParamStr(0)) + formdata, fmCreate);
  try
    fs.WriteComponent(self);
  finally
    fs.free
  end;
end;

procedure TForm1.FormCreate(Sender: TObject);
var
  filename: string;
  fs: TFileStream;
  i: integer;
begin
  filename := ExtractFilePath(ParamStr(0)) + formdata;
  if fileExists(filename) then
  begin
    for i := ComponentCount - 1 downto 0 do
      Components[i].Free;
    fs := Tfilestream.create(filename, fmOpenRead or fmShareDenyWrite);
    try
      fs.ReadComponent(self);
      button1.enabled := false;
    finally
      fs.free
    end;
  end;
end;

initialization
  RegisterClasses([TButton, TEdit]);
end.

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