[dws-developer] VclWrappers and Destructors (Andreas?)

[Mark <mnm...@co...>]

Andreas & others,

Mark here. I've been quiet, I know. I was trying to add fix the 
destructor issue that we discussed some time ago. Here is the problem as 
I see it. Any insight or direction is appreciated.

Taken from dws2ClassesLib.pas:
<DELPHI>
   TMeth_TFileStream_Create = class(TAnonymousMethod, ICallable)
     procedure Execute(var ExternalObject: TObject); override;
   end;

[...]

procedure TMeth_TFileStream_Create.Execute;
begin
   //constructor TFileStream.Create(const FileName: String; Mode: Integer);
   if not Assigned(ExternalObject) then
     ExternalObject := TFileStream.Create(Info['FileName'], Info['Mode']);
end;
</DELPHI>

The problem is that the script object's constructor implemented through 
the TMeth_TFileStream_Create class. The real issue is that if the 
instance is ALREADY created (ie. RegisterExternalObject) then we DON'T 
want the script object to destroy it when it scopes out. I don't have 
any way to add a flag to say "Yes, I want this instance auto-cleaned up."

I've looked into changing some code in dws2Functions.pas for 
TAnonymousMethod.Call(...) to test if we are about to call a constructor 
and the ExternalObject goes from "nil" to "not nil" then flag the 
IScriptObject as needing to free the class. However, this is a nasty 
hack and is very ugly. I hate ugly code and I hate even more writing it!

If you can point me to a better solution I would really appreciate it.

I really do want to fix it the right way. It is an issue for me when you 
have a TFileStream and the Delphi object instance isn't freed until the 
Host application closes. It ends up holding locks on the file.

-Mark E.