Registering class in DLL.

The class is registered only in the class list of the DLL module. The application class list (which is a different one) doesn't have this class.

If your DLL and your application is written in exactly the same Delphi version, you can export a function from your dll like this:

function GetClass : TPersistentClass;
begin
  result := TMyClass;
end;

exports GetClass;

Then in your application do this:

var GetDllClass : function GetClass : TPersistentClass = nil;

var dll : dword;
begin
  dll := LoadLibrary('your.dll');
  GetDllClass := GetProcAddress(dll, 'GetClass');
  // Now you can call GetDllClass

Regards, Madshi.

correction:

var GetDllClass : function : TPersistentClass = nil;

Madshi,

Thanx, it's look good. Is it possible to register class from DLL to main application classes list? I try to explain what I need.

Usually, DB application, have a lot of editing/inserting records forms. My idea is very simply. Every table have predefined form for editing/inserting. I have a list of matches between table name and form classname (it stored in database). Due to this, there is an opportunity to open the forms of editing/inserting from any place of the application without including into "uses ..." clause.

Last two years it work Ok, but now, I'm trying to put some forms into DLL's. Is it possible to do this avoiding of modification any of my service units?

Regards,
Igor

Yes Madshi. The great idea is to export procedures from main App to DLL:). You are realy tricky.

initialization
  AppModule:= GetModuleHandle(nil); ??;)

Thanx for help, I try it as soon as possible, but points is yours right now.

Cheers,
Igor.

 AppModule:= GetModuleHandle(nil);

This gives you the module handle (= instance handle) of the application, which is needed to call GetProcAddress.

I tried the code looks like :

unit UFAdminSFCSTPPRDCDBGDG;

interface

uses
  UAdminSFCSTPPRDCDBGDG, Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms, DB, InvokeRegistry,
  Dialogs, RzStatus, RzButton, StdCtrls, Mask, RzEdit, RzLabel, RzTabs, ExtCtrls, RzPanel, CodeSiteLogging, RzCommon;

type
  TFAdminSFCSTPPRDCDBGDG = class(TFrame)
    Panel1012111010101011101010101110101710: TRzPanel;
    PC101211101010101110101010111010171010: TRzPageControl;
    Tab10121110101010111010101011101017101010: TRzTabSheet;
    Panel1012111010101011101010101110101710101010: TRzPanel;
    PC101211101010101110101010111010171010101010: TRzPageControl;
    Tab10121110101010111010101011101017101010101010: TRzTabSheet;
    RzLabel31: TRzLabel;
    RzLabel47: TRzLabel;
    IN101211101010101110101010111010171010101010101010: TRzEdit;
    Tmb1012111010101011101010101110101710101010101010: TRzBitBtn;
    Tab10121110101010111010101011101017101010101011: TRzTabSheet;
    RzLabel76: TRzLabel;
    RzLabel77: TRzLabel;
    Tmb1012111010101011101010101110101710101010101110: TRzBitBtn;
    IN101211101010101110101010111010171010101010101011: TRzEdit;
    Tab10121110101010111010101011101017101010101012: TRzTabSheet;
    Tmb1012111010101011101010101110101710101010101210: TRzBitBtn;
    RzPanel6: TRzPanel;
    RzPanel18: TRzPanel;
    RzLabel78: TRzLabel;
    Tab10121110101010111010101011101017101011: TRzTabSheet;
    Panel1012111010101011101010101110101710101110: TRzPanel;
    Panel101211101010101110101010111010171010111010: TRzPanel;
    RzProgressStatus5: TRzProgressStatus;
    RzPanel27: TRzPanel;
    RzLabel79: TRzLabel;
    PC101211101010101110101010111010171010111010: TRzPageControl;
    Tab10121110101010111010101011101017101011101010: TRzTabSheet;
    Tmb1012111010101011101010101110101710101110101010: TRzBitBtn;
    Tmb1012111010101011101010101110101710101110101011: TRzBitBtn;
    Tmb1012111010101011101010101110101710101110101012: TRzBitBtn;
    Tmb1012111010101011101010101110101710101110101013: TRzBitBtn;
    Tmb1012111010101011101010101110101710101110101014: TRzBitBtn;
    Tmb1012111010101011101010101110101710101110101015: TRzBitBtn;
    Tmb1012111010101011101010101110101710101110101016: TRzBitBtn;
    Panel101211101010101110101010111010171010111011: TRzPanel;
    Tab10121110101010111010101011101017101012: TRzTabSheet;
    Panel1012111010101011101010101110101710101210: TRzPanel;
    Panel101211101010101110101010111010171010121010: TRzPanel;
    PS10121110101010111010101011101017101012101010: TRzProgressStatus;
    RzPanel59: TRzPanel;
    RzLabel80: TRzLabel;
    PC101211101010101110101010111010171010121010: TRzPageControl;
    Tab10121110101010111010101011101017101012101010: TRzTabSheet;
    Tmb1012111010101011101010101110101710101210101010: TRzBitBtn;
    Tmb1012111010101011101010101110101710101210101011: TRzBitBtn;
    Tmb1012111010101011101010101110101710101210101012: TRzBitBtn;
    Panel101211101010101110101010111010171010121011: TRzPanel;
    RzPanel60: TRzPanel;
    RzPanel61: TRzPanel;
    RegIniFile: TRzRegIniFile;
  private

    { Private declarations }
  public
    { Public declarations }

    constructor Create(EKO : TComponent); override;
  end;

var
  FAdminSFCSTPPRDCDBGDG : TFAdminSFCSTPPRDCDBGDG;

implementation

{$R *.dfm}

constructor TFAdminSFCSTPPRDCDBGDG.Create(EKO: TComponent);
begin
  inherited create;
end;

CodeSite.ExitMethod( 'procedure : AssignDoubleBuffered' );
end;
var
  RegisterClass : procedure (AClass: TPersistentClass) = nil;
  UnregisterClass : procedure (AClass: TPersistentClass) = nil;
  appModule : dword;

initialization

appModule := GetModuleHandle(nil);
RegisterClass := GetProcAddress(appModule, 'RegisterClass');
UnregisterClass := GetProcAddress(appModule, 'UnregisterClass');
RegisterClass(TFAdminSFCSTPPRDCDBGDG);

finalization

 UnRegisterClass(TFAdminSFCSTPPRDCDBGDG);

end.

But still error with raise error message : EAccessViolation
Any solution or advise please ?

thanks for advance