Title: use forms declared in DLL by an executable?
{
In the example that follows the exe only sees a totally "virtual
abstract" interface to the object as is being exported from the dll
but it still can create the object and use it.
Of course the exe can not see or execute any methods declared in the
exe but that is the whole purpose of implementing them in a custom dll
to begin with.
Im folgenden Beispiel sieht die Exe-Datei nur ein total "virtuelles, abstraktes"
Interface zum Objekt, welches aus der Dll importiert wird aber es
kann doch dieses Objekt erzeugen und es gebrauchen.
}
// Example code:
program Dlloader;
uses
Sharemem,
Forms,
exeunit1 in 'exeunit1.pas' {Form1},
DllIntfu in 'DllIntfu.pas';
{$R *.RES}
begin
Application.Initialize;
Application.CreateForm(TForm1, Form1);
Application.Run;
end.
//--------------------------
unit DllIntfu;
interface
type
TDllobject = class
protected
function Get_UserName: string; virtual; abstract;
procedure Set_UserName(Value: string); virtual; abstract;
public
property UserName: string read Get_UserName write Set_UserName;
end;
TDllobjectClass = class of TDllobject;
implementation
end.
//---------------------------
unit exeunit1;
interface
uses
Windows, Messages, SysUtils, Classes, Graphics,
Controls, Forms, Dialogs, DllIntfu, StdCtrls;
type
TForm1 = class(TForm)
Button1: TButton;
procedure Button1Click(Sender: TObject);
private
{ Private declarations }
public
{ Public declarations }
end;
var
Form1: TForm1;
implementation
{$R *.DFM}
type
TDllfunc = function: TDllobjectClass;
stdcall;
procedure TForm1.Button1Click(Sender: TObject);
var
i: DWORD;
fHandle: THandle;
fDllfunc: TDllfunc;
fDllobject: TDllobject;
fUserName: string;
begin
fHandle := LoadLibrary('UserName.dll');
if (fHandle 0) then
begin @fDllfunc := GetProcAddress(fHandle, 'Dllfunc');
if Assigned(@fDllfunc) then
begin
i := 255;
SetLength(fUserName, i);
GetUserName(PChar(fUserName), i);
fUserName := StrPas(PChar(fUserName));
fDllobject := fDllfunc.Create;
fDllobject.UserName := fUserName;
ShowMessage(fDllobject.UserName);
fDllobject.Free;
end;
FreeLibrary(fHandle);
end;
end;
end.
//-------------------------------
library UserName;
uses
Sharemem,
Sysutils,
DllIntfu;
type
TCustomDllobject = class(TDllobject)
private
fUserName: string;
function Getfilecount: Integer;
protected
function Get_UserName: string; override;
procedure Set_UserName(Value: string); override;
end;
TCustomDllobjectclass = class of TCustomDllobject;
function TCustomDllobject.Getfilecount: Integer;
var
doserr: Integer;
fsrch: TSearchRec;
begin
Result := 0;
doserr := FindFirst('*.*', faanyfile, fsrch);
if (doserr = 0) then
begin
while (doserr = 0) do
begin
if (fsrch.attr and faDirectory) = 0 then
Inc(Result);
doserr := findnext(fsrch);
end;
FindClose(fsrch);
end;
end;
function TCustomDllobject.Get_UserName: string;
begin
Result := 'You signed on as ''' + fUserName + '''' +
' and there ' + IntToStr(Getfilecount) +
' files in this directory.';
end;
procedure TCustomDllobject.Set_UserName(Value: string);
begin
fUserName := Value;
end;
function Dllfunc: TCustomDllobjectClass; stdcall;
begin
Result := TCustomDllobject; // class type only
end;
exports
Dllfunc name 'Dllfunc';
begin
end.