Here's an odd one. I wanted to call the OnCloseQuery of a form, if it has one. I don't want to actually close it. But I can't, it seems, just call it directly. Any reason why?

procedure TfrmAdminWelcome.ConfirmClose;
var
   Sender: TObject;
   bClose : Boolean;
   xEvent : TCloseQueryEvent; //  = function (Sender: TObject): Boolean of object;
begin
   if assigned(m_xActiveForm) then
   begin
       if (assigned(m_xActiveForm.OnCloseQuery)) then
       begin
      // this version works - I copy it to a local and can call it
           xEvent := m_xActiveForm.OnCloseQuery;
           bClose := xEvent(self);
           if not bClose then
               raise Exception;

      // these versions won't compile
//            bClose := TForm(m_xActiveForm).OnCloseQuery(self);
//            if (not m_xActiveForm.OnCloseQuery()) then
//                Abort;
       end;
   end;
end;

It's not critical, I'd just like to understand it.

--

Matthew Jones

On 3/13/2019 2:40 PM, Matthew Jones wrote:
> Here's an odd one. I wanted to call the OnCloseQuery of a form, if it has one. I don't want to actually close it. But I can't, it seems, just call it directly. Any reason why?
....
> It's not critical, I'd just like to understand it.
>

Why not just call Close ?

As long as your OnCloseQuery returns false it should not actually close.

Otherwise i think this is because this is an internal implementation.

More interesting question is why would you want to call it direct to
begin with !?

Raul

On 3/13/2019 8:22 PM, Raul wrote:
> Otherwise i think this is because this is an internal implementation.

Never mind - i totally misread the question.

It looks like a limitation of the compiler. m_xActiveForm.OnCloseQuery
should be callable IMHO - i suspect due to it being a property so it's
not resolving to TCloseQueryEvent properly but need Tim to answer this
one as as its pure speculation.


Raul

It's shortcoming of the compiler. I first encountered it when I tried to skip calling of inherited constructor in a class constructor and call a constructor of a predecessor of the class ancestor, i.e. instead of calling
inherited Create;
call to
TAncestorsPredecessor.Create;

Raul wrote:

> It looks like a limitation of the compiler.

Indeed, so long as it isn't me being daft. 8-)

Thanks both.


--

Matthew Jones

Matthew,

<< Here's an odd one. I wanted to call the OnCloseQuery of a form, if it has one. I don't want to actually close it. But I can't, it seems, just call it directly. Any reason why? >>

I know that this thread is old, but for the record, EWB 3's compiler won't have issues like this anymore.  I've taken the time to re-do the front-end of the compiler, also, and I've fixed various issues with symbol resolution, as well as more esoteric things like this where the current compiler has a hard time: calling method properties, calling method instances that are returned from other functions/methods, or calling method instances that are stored in arrays.

Tim Young
Elevate Software
www.elevatesoft.com