[Jprogramming] Classes & OOP in J

[Sherlock, Ric]

Amoung the rest of things I'm trying to get my head around, I'm starting
to try & understand OOP & how it works in J. As part of this I was
looking at Oleg's nifty SQLite browser (~addons\data\sqlite\browser.ijs)
that comes as part of his SQLite addon in JAL.
 
My question is about creating and destroying instances of a class
(please feel free to correct me if I get some of the terminology wrong).

As far as I can see when an instance of the psqlitebr class is created,
it creates an instance of the jzgrid class.
 
Then when the connect method is run with an non-zero length y, an
instance of the psqlite class is created.

All good so far I think.

When the form is closed (via f_close or f_exit) the destroy method runs
and destroys the instance of the psqlite class (by running connect'')
and the instance of psqlitebr (by running codestroy''), but as far as I
can see the instance of the jzgrid class doesn't get destroyed.

Is there a reason for this?