Question

I have a form (form2) and I implemented the following PUBLIC method:

function ShowInterface(i:integer):boolean;

This form is in a package that will be DYNAMIC LOADED. Now I want to instantiate this form (form2) and execute the method above.

Important: I can’t reference form2’s unit in form1.

I tryed this code, but it never finds “ShowInterface” pointer (returns nil).

procedure TfrmForm1.Button1Click(Sender: TObject);
var
  PackageModule: HModule;
  AClass: TPersistentClass;
  ShowInterface: function (i:integer):boolean;
  frm: TCustomForm;
begin
  PackageModule := LoadPackage('form2.bpl');
  if PackageModule <> 0 then
  begin
    AClass := GetClass('TfrmForm2');
    if AClass <> nil then // <<-- FINE!! IT FINDS OUT 'TfrmForm2' in 'form2.bpl')
    begin
      frm := TComponentClass(AClass).Create(Self) as TCustomForm;
      ShowInterface := frm.MethodAddress('ShowInterface'); // <<-- HERE!! ALLWAYS RETURNS "NIL"
      if @ShowInterface <> nil then
        ShowInterface(1);
      // but if I call frm.Show, it works fine. frm is "loaded"!!!

      frm.Free;
    end;
    DoUnloadPackage(PackageModule);
  end;
end;

Thanks in advance.

Answer 1

MethodAddress only works for published methods. Move it to the published section and it should work.

Or, if you have Delphi 2010, the extended RTTI offers a way to find public methods by name. (Or other visibility levels, if you change it from the default.)