How to .Free a non-modal form?

[Tom F 80]

I create a non-modal form like this:
 

procedure TForm1.Button1Click(Sender: TObject);
begin
  FNonModalForm := TForm2.Create(Self);
  FNonModalForm.Show;
end;

What's a good way to have a non-modal Form2 signal its owner Form1 that the non-modal form has been closed by the user so the owner can free Form2?

AFAIK, it can't be done in a callback from Form2.FormClose because that's too early for the owner Form1 to free Form2.

 

Send a Windows message to the owner form?

[Attila Kovacs 617]

in OnClose Action := caFree;

[Tom F 80]

Is Assigned(FNonModalForm) false after that statement? 

[Attila Kovacs 617]

A TForm or descendant has an event OnClose. 

 

Quote

procedure TForm2.FormClose(Sender: TObject; var Action: TCloseAction);
begin

  Action := caFree;

end;
 

Thats it. No further interaction needed.

 

[Remy Lebeau 1255]

2 hours ago, Tom F said:

Is Assigned(FNonModalForm) false after that statement?

No.  You have to reset it manually.

1 hour ago, Attila Kovacs said:

A TForm or descendant has an event OnClose. 

 

Thats it. No further interaction needed.

Unless the parent form needs to reset its FNonModalForm variable, in which case you would need to move the OnClose handler to the parent form instead, eg:

procedure TForm1.Button1Click(Sender: TObject);
begin
  if FNonModalForm = nil then
  begin
    FNonModalForm := TForm2.Create(Self);
    FNonModalForm.OnClose := NonModalFormClosed;
  end;
  FNonModalForm.Show;
end;

procedure TForm1.NonModalFormClosed(Sender: TObject; var Action; TCloseAction);
begin
  FNonModalForm := nil;
  Action := caFree;
end;

 

Edited January 15, 2021 by Remy Lebeau

[Attila Kovacs 617]

@Remy Lebeau ah, right, I missed that part, I just read the title.

[Tom F 80]

Thanks, Remy!  That's what I needed.  It never occurred to me to hook the OnClose event itself!